Table of Contents Answer Key ............................................................................................................................. 4 Audioscripts.............................................................................................................................. 13 Answer Key ............................................................................................................................... 15 Audioscripts .............................................................................................................................. 24 Answer Key .............................................................................................................................. 27 Audioscripts ............................................................................................................................. 37 Book 1 Answer Key What were your duties at your previous job? I designed control mechanisms for forklifts. Unit 1 1 Suggested Answers 1 A mechanical engineer has a variety of responsibilities. Mechanical engineering includes designing machines. Unit 2 Mechanical engineers also test and manufacture machinery. When they encounter problems, it is their job 1 Suggested Answers to assess issues and determine what went wrong. 1 Bearings are very important for supporting shafts. They 2 A mechanical engineer has a number of important help bear weight and direct motion. In addition to qualities. A qualified mechanical engineer has at least a allowing motion in the appropriate direction, they also bachelor’s degree in an engineering field. Mechanical prevent shafts from moving in undesired directions. engineers must understand all of the important physical Without bearings, shafts might move uncontrollably, properties of machines, like power transmission. Since preventing useful work from being performed. the field of mechanical engineering is so broad, many 2 There are several different types of bearings. The mechanical engineers specialize in a particular branch. primary types are rolling contact bearings and journal bearings. Rolling contact bearings come in a number of 2 Type of Gear Features varieties. Ball bearings, straight roller bearings, and tapered roller bearings all allow radial motion. Thrust Responsibilities designing and building machines, assessing and improving machines, roller bearings and tapered roller bearings both allow inventing new hardware thrust motion. Qualifications a degree in engineering 2T 3T Areas of study physics, kinematics, manufacturing, 2 1 F machine testing 3 A tapered roller bearing E ball bearing B straight roller bearing F thrust roller bearing 3 A power transmission D test G assess C journal bearing G axial B mechanical engineer E manufacture D rolling contact bearing H radial C hardware F broad 4 1 A inner race B outer race 2 A sleeve B bearing 4 1 specialize in 2 improve 3 design 5 5 Suggested Answer Mechanical engineers have to study many different topics to be proficient in their field. A college education in engineering is essential. It is needed in order to specialize. Suggested Answer Thrust roller bearings cannot support radial forces. They are only designed for thrust motion. 6 1A 6 1T 2T 7 7 1 interview 2 worked for 2C 3F 3 job duties 4 improve 5 design 6 new engines 1 do me a favor 2 bearings 3 straight roller bearings 4 ball bearing 5 inner race 6 head out 8 Suggested Answer 8 Suggested Answer A: Could you please go to the hardware store? A: Hi, I’m John Smith. I’m here to interview for the position of B: Of course. What do you need? mechanical engineer. A: I need two ball bearings and a straight roller bearing. B: Tell me about your work experience. B: I can do that. A: I worked for Osterbell Incorporated for six years. A: I need them by this afternoon. B: What were your duties at your previous job? B: I’ll head out right now. A: I designed control mechanisms for forklifts. B: Were you involved in manufacturing them? 9 Suggested Answer A: Not directly. Expense Report B: If we hire you, you’ll be working in manufacturing as well Date: 7/15 as design. Purchase made by: Vicki Marteney What did you purchase? I purchased a straight roller bearing 9 Suggested Answer and two ball bearings. What position are you applying for? Why did you purchase them? The straight roller bearing is for a Mechanical engineer new project that requires radial motion. The ball bearings are to What is your educational background? replace broken ones. I have a college degree in mechanical engineering. Total Cost: $63.89 4 Answer Key Book 1 Answer Key Unit 3 1 Suggested Answers 1 Couplings are very useful components. They connect shafts together to transmit power. In addition to transmitting power, they can connect shafts while still allowing for a certain measure of misalignment. They make it easy to disconnect shafts for maintenance. Some couplings can also provide mechanical flexibility. 2 There are two major types of coupling: rigid and flexible. Rigid couplings hold shafts in perfect alignment, reducing wear and improving the overall performance and longevity of the machine. A common rigid coupling is a sleevestyle coupling. Flexible couplings allow for misalignment and offset. They also absorb vibrations and reduce machine noise. A common flexible coupling is a 2 beam coupling. 1 There are a number of different gears for different purposes. The most common and easily recognizable gear is a spur gear. Spur gears are cut from a cylinder and have teeth that protrude straight out radially. Helical gears have teeth that wind around the gear in a spiral pattern. Bevel gears mesh together at right angles. Bevel gears can have either helical or spur teeth. 2 Rack and pinion type gears have special characteristics. Most gears work exclusively in rotational motion. Rack and pinion gears convert rotational motion to linear motion. The pinion is a standard round gear, while the rack is a linear, toothed track on which the pinion moves. As the teeth mesh together, the pinion travels along the rack. Type of Gear Features Spur Gear 2 1F 2T 3 A transmit B output shaft C input shaft D sleeve-style coupling E offset F coupling 4 1A 3B has teeth projecting towards or away from the center has one continuous tooth 3T Helical Gear G beam coupling Rack and Pinion Gear 3 A tooth B pinion 5 Suggested Answer 4 1 A gear Flexible couplings allow for slight offset and misalignment. This can reduce vibrations and machine noise. This means perfect alignment is not necessary to transmit power. 5 Suggested Answer 2B 6 1 C 7 1 coupling 2 output shafts 5 flexible 6 beam coupling A: I think a sleeve-style coupling would work best. B: I agree. It’s the simplest solution. 9 Suggested Answer Project Progress Report Project #: 981b List changes to the project: We replaced coupling 23B with a sleeve-style coupling. Reason for changes: We originally planned to use a beam coupling. But the shafts have a slight offset. We have to use a rigid coupling instead. Unit 4 1 Suggested Answers B rack 6 1F 7 1 gear 2 bevel gears 8 Suggested Answer 8 Suggested Answer A: I noticed a problem in this design. B: What’s wrong with it? A: This beam coupling won’t work. It’s too flexible. B: You’re right. It looks like we need to align the shafts. A: Yes. We’ll have to use a rigid coupling instead. B: What do you recommend? C worm gear D mesh E spur gear F worm 2 A bevel gear B helical gear Rack and pinion gears convert rotational motion into linear motion. 2A 3 offset 4 It’ll break converts rotational motion to linear motion 2F 3T 3 I’d like to 4 teeth 5 mesh 6 helical gears A: How are those plans coming along? B: We still need to decide what gears to use for transmission 6D. A: We should use spur gears. They’re cheap and easy to install. B: That’s true. But I’d like to use helical gears. A: Are you concerned about noise? B: Yes. The helical gears will also reduce excess vibrations. A: You’re right. Let’s use helical gears. B: Sounds like a plan. 9 Suggested Answer Part Number: 6D Type of Hardware: Helical gear Why was this hardware selected? Helical gears mesh more smoothly than spur gears. They will reduce noise and unnecessary vibrations. Answer Key 5 Book 1 Answer Key Unit 5 1 Suggested Answers 1 Belt drives are a very common type of drive. V-belts are the standard belts for many different purposes. The belts are wedge-shaped and the force of their own motion holds them in place on the sheaves. However, v-belt slippage still occurs. Timing belts have grooves to prevent slippage. 2 Timing belts and chain drives are both used when synchronous rotation is necessary. The grooves on a timing belt ensure that the belt will not slip. Similarly, the links on a chain drive keep the drive running in perfect time. Synchronous rotation is used when different parts must occupy the same spaces at different times. When the timing belt in an interference engine breaks, many engine parts collide and break. 2 1 C 2D 3 A synchronous rotation B chain drive C sheave 4 1 groove Maintenance Date: 8/12 Part Name: Timing Belt Describe the maintenance: The timing belt is worn. The belt needs to be replaced. How soon is the maintenance needed? The current belt will not last more than another two months. Unit 6 1 Suggested Answers 1 Engineers use a number of basic hand tools. A typical toolbox includes different types of screwdrivers for attaching and tightening parts together. Hammers are used to attach parts securely, or sometimes to break them apart. Saws are used to cut pieces of material into smaller pieces. 2 A Phillips screwdriver and a slotted screwdriver both serve the same purpose, but they fit into different types of screws. A screw with a single, long indentation along the top requires a slotted screwdriver. A screw with an indentation in the shape of a cross, however, requires a Phillips screwdriver. 3A 2 belt drive D v-belt E wedge angle F timing belt G link 3 slippage 2 1C 3 A slotted screwdriver B calipers C vice 4 1 A ball peen hammer 2 A Pliers 5 Suggested Answer Timing belts have grooves to ensure synchronous rotation. They prevent slippage and keep crucial pieces of machinery from interfering with each other. 6 1F 2F 5 3T 7 1 belt drive 2 slippage 3 v-belt 4 sheave 8 Suggested Answer 9 Suggested Answer 6 Answer Key 3B D box wrench E socket wrench F pliers G hacksaw H Phillips screwdriver B hacksaw B Sledge hammers Suggested Answer The new project requires additional slotted screwdrivers instead of Phillips screwdrivers. 5 break down 6 I’d say A: I just finished working on that chain drive. B: What was wrong with it? A: One of the links was cracked. I had to replace the chain. B: How does the rest of the engine look? A: There’s a timing belt that should be replaced soon. B: Good to know. We don’t want the engine to break down. A: I’d say it’ll be safe for another month or two. After that, we need a new one. B: I’ll put it on the maintenance schedule. In the meantime, keep an eye on it. 2A 6 1T 7 1 our tools 2 screwdrivers 8 2F 3F 3 wrong 4 screws 5 socket wrenches 6 order Suggested Answer A: I received your email. Which tools do you think we need the most? B: We definitely need some Phillips screwdrivers. A: I don’t understand. What’s wrong with the old screwdrivers? B: We have new screws that the old screwdrivers won’t fit. A: I understand now. Is there anything else we need? B: We also want to order new box wrenches. The old ones Book 1 Answer Key B: Exactly. Our current lathe doesn’t shape materials as well as it used to. A: I’ll place the order this afternoon. are missing. A: I’ll order all those tools tomorrow. 9 Suggested Answer Equipment requested: Phillips screwdrivers Box wrenches Why is this equipment needed? Our current slotted screwdrivers don’t fit the screws. The old ones are missing. 9 Suggested Answer Product requested: Lathe Do we already have this type of product? Yes Why do you want to order this product? A new lathe will be more precise than our current. No Unit 7 Unit 8 1 Suggested Answers 1 The difference between a hand tool and a machine tool is the power source. When someone uses a hand tool, the tool is operated solely by the user. When someone uses a machine tool, the user might guide the tool, but a machine performs most of the work. 2 A drill press is a common machine tool that is used to create precise holes in surfaces. Another machine tool is the band saw, which is used to cut tough materials like metal and plastic. Some machine tools are used to hone and finish materials. These include mills, lathes, and honing machines. 2 1T 3 A gear shaper B honing machine 4 5 2F 3F E band saw F drill press B CNC mill B lead screws Suggested Answer A mill shapes and finishes rough surfaces. It might make a surface flat or create grooves or holes. It is a reliable machine tool. A CNC mill is operated with new technology. 1C 7 1 definitely need 2 machine tools 1 Adding and subtracting are related operations, but their effects are opposite. When two positive quantities are added, the result is a larger quantity. 2 Multiplying and dividing are reverse operations. If A multiplied by B equals C, then C divided by B equals A. While multiplication adds a quantity a certain number of times, division splits a quantity apart a certain number of times. Multiplication is sometimes used to achieve the same result as division. This process involves multiplying a quantity by a fraction instead of a whole number. 2 1T C mill D lathe 1 A broach 2 A machine tools 6 1 Suggested Answers 2A 3 new mill 4 really advanced 5 faster 6 place the order 8 Suggested Answer A: Did you see the new product catalogue? B: Yes. We definitely need some new tools. A: Do you have any machine tools in mind? B: I suggest that we order a new lathe. A: Some of those new ones look really precise. 2F 3T 3 1 A multiplied by 2 A minus B plus B over 4 1 subtract 5 Suggested Answer 2 equals 3 A divided by 3 hundred 4 times B times 5 add “One thousand five hundred” can also be expressed as “fifteen hundred”. 6 1D 2B 7 1 I asked for 2 centimeters long 8 Suggested Answer 3 I subtracted 4 add two 5 I calculated 6 Just cut some A: Where are the tiles I asked for? B: They’re on the workbench. A: These are only ten centimeters across. B: That’s right. I added two centimeters more than the previous tiles, like you asked. A: I wanted you to multiply by two. Answer Key 7 Book 1 Answer Key B: So they’re supposed to be sixteen centimeters? I’m really sorry for the mix-up. 9 A: Let’s measure the new components. B: Sure. What do we need to measure? A: Start with the coupling. How much does it weigh? B: It looks like 0.6. A: Is that a metric or imperial measurement? B: That’s an imperial measurement. It’s 0.6 pounds. A: That makes sense. What’s that in kilograms? B: So 0.6 times 0.45 equals 0.27 kilograms. Suggested Answer Hi Lou, There’s a problem with the tiles. I need some that are sixteen centimeters across. However, these are ten centimeters across. I think you used the wrong operation when you calculated the measurements. You were supposed to multiply by two centimeters to the previous measurement. Instead, you added two. Please watch out for these errors in the future. Nell Unit 9 1 Suggested Answers 1 In the metric system, small weights are expressed in grams. Larger weights might appear in kilograms. One kilogram equals 1,000 grams. In the imperial system, smaller weights often appear in ounces. An ounce is not as small as a gram. Larger weights appear in pounds, which are each equal to sixteen ounces. 2 In the metric system, quantities are converted between units using multiples of ten. Larger units are multiplied to calculate measurements in smaller units. For example, to convert meters into centimeters, the quantity is multiplied by 100. Twelve meters times 100 equals 1200 centimeters. Conversely, 500 centimeters divided by 100 equals five meters. 2 1F 3 1 A feet 4 8 Suggested Answer 2T Measurements of: Length There are 0.3 meters in a foot. Three meters equals 10 feet. Measurements of: Weight There are 28.35 grams in an ounce. Half of an ounce equals 14.175 grams. Unit 10 1 Suggested Answers 1 In the imperial system, many volume measurements are expressed in gallons. When a smaller unit is needed, measurements can be expressed in fluid ounces as well. There are 128 fluid ounces in a gallon. In the metric system, many quantities are expressed in liters. Very small amounts are measured in milliliters, which are also called cubic centimeters. 2 The Celsius system and the Fahrenheit system both measure temperature, but they are based on different boiling and freezing temperatures. In the Celsius system, water freezes at zero degrees and boils at 100 degrees. In the Fahrenheit system, water freezes at 32 degrees and boils at 212 degrees. 3T B grams Metric Units meter kilogram 2 A metric B imperial Imperial Units Types of Measurements 2 1D ounce pound 3 A Celsius B convert weight length 4 5 Suggested Answer Someone can convert meters into feet by dividing the quantity of meters by 0.30. 6 1C 9 Suggested Answer 2D 1 Let’s measure 2 long is it 8 Answer Key 3 metric or imperial 4 meters 5 in feet 6 divided by 1 liters 3C C fluid ounce D temperature 2 gallon 3 Volume E milliliter F Fahrenheit 4 cubic centimeter 5 Suggested Answer The formula for converting Celsius to Fahrenheit is: ºC x 9/5 + 32=ºF. 6 7 2A 1F 2F 3T Book 1 Answer Key 7 1 made the conversions 2 what’s the volume 3 metric measurement 4 gallons 5 what about 6 degrees Celsius 5 Suggested Answer In the SI, force is calculated in newtons. The formula is: N=kg x m / s2. 8 Suggested Answer A: Do you have the new measurements for the Grayline project? B: Yes, I just made the conversions. A: So what’s the volume of the chamber? B: Let me see. That was 3.6. A: Now that’s an imperial measurement, right? B: Yes. It was 102 milliliters. That divided by 28.41 equals about 3.6 fluid ounces. 9 Suggested Answer Hi Kevin, Here are the measurement conversions that you requested. Volume: There were 102 milliliters in the chamber. To convert that into fluid ounces, I divided that number by 28.41 which resulted into 3.6 fluid ounces. I’ll remember to use the correct system next time. Lisa Unit 11 1 Suggested Answers 1 Base units and derived units are both used to measure properties in the SI. Base units include a small group of simple units, such as the kilogram and the meter. They are individual measurements. Derived units are more complex, and are calculated by applying a formula to one or more base units. 2 Some derived unis require measurements from just one base unit. However, they are still derived because a formula must be applied to the base unit. For example, a cubic meter is a unit of volume. The number of meters on one side of a cube is raised to the third power: m3. To calculate degrees Celsius, 273.15 is subtracted from the Kelvin measurement. No other units of measurement are needed. 2 1F 3 4 2F 3T A joule B derived unit C newton D pascal E base unit Systems of Measurement SI Units of Measurement kelvin cubic meter Properties that are Measured force mass 6 1C 2A 7 1 determine the force 3 kilograms times meters 5 so similar 2 formula 4 measure energy 6 base units 8 Suggested Answer A: I need some help with this physics assignment. B: What are you supposed to do? A: I need to determine the pressure. That means I calculate it in pascals, right? B: Yes. Do you remember the formula? A: It’s kilograms times meters over seconds squared. B: No, that’s the formula for newtons. Those measure force, not pressure. A: These formulas look so similar. B: They use the same base units. You want kilograms over meters times seconds squared. 9 Suggested Answer 1. Energy is calculated in joules. You need the following base units: kilograms, meters, and seconds. Formula: J=kg x m 2 / s2 2. Force is calculated in newtons. You need the following base units: kilograms, meters, and seconds. Formula: N=kg x m / s2 3. Volume is calculated in cubic meters. You need the following base unit: meters. Formula: m3 Unit 12 1 Suggested Answers 1 Very large and very small numbers can be difficult to work with in decimal form. Since they require many digit places, they are easily misread. They can also take up large amounts of space on a page. Scientific notation provides a more consistent and concise way to express these numbers. It shows a quantity times ten raised to a particular power. 2 If a quantity has too few significant figures, the results of a formula could be inaccurate. Even if the error is small, it is likely to be magnified when the quantity is multiplied. If significant figures are omitted over the Answer Key 9 Book 1 Answer Key a quantity in relation to the number 100. A decimal number is similar, but the quantity appears after a zero and a decimal point instead. 2 Improper fractions and mixed numbers both express quantities that are greater than one, but they appear in different formats. A mixed number starts with the highest whole number that the quantity contains. Then, a fraction indicates the remaining parts that are less than one. For example, 2 1/3 is a mixed number. The same quantity can also be expressed strictly as a fraction, which is the improper fraction: 7/3. course of several steps, the rounding errors could be substantial. 2 1B 2A 3B 3 A significant figure B to the nth power 4 1 tenths 2 cubed C thousandth D squared 3 rounding error 4 trailing zero E scientific notation F hundredth 5 exponent 5 Suggested Answer If the wrong exponent is used in an equation, it can cause serious errors in the results of the project. 2 1T 6 1T 2F 3F 7 1 not right 2 a thousand joules 3 way too high 4 cubed 5 wrong exponent 6 really careful 8 SuggestedAnswer A: Something’s not right in this equation. B: I checked it twice. A: The energy of this system should be 4,890 joules. Your result came to about 4,900. B: That’s more than ten joules off. I wonder what I did wrong. A: Let’s take a look. I see. You rounded the meters to the tenths instead of the thousandths. B: So I used the wrong number of significant figures. A: Exactly. You have to be really careful about this. That kind of error could be disastrous. 9 Suggested Answer Hi Paul, Your report contains an error. Please correct the error and submit the report again. Error: The equation was wrong. The meters were rounded to the tenths instead of the thousandths. Result of the error: The joules appeared to be 4,900. Corrected quantity: The correct number should be 4,890. Lenore Unit 13 1 Suggested Answers 1 Quantities that are smaller than one appear in a few forms. Fractions are a common way to express these quantities. They show a quantity in terms of the number of parts out of a whole that it occupies. A percent shows 10 Answer Key 2T 3 A quantity B reduce 3F C improper fraction D mixed number 4 1 A percent 2 A decimal number E out of F point B fraction B whole number 5 Suggested Answer An improper fraction (e.g. 13/4) can either be converted into a mixed number (e.g. 3 1/4) or a decimal number (e.g. 3.25). 6 1D 2B 7 1 working better 2 What fraction 3 nine out of ten 4 pretty good 5 eight percent 6 coming along 8 Suggested Answer A: Do you have the report on the generator test? B: Yes. The prototypes are working better than we expected. A: That’s great! Does the fuel last longer? B: Yes. It takes half a day to use one unit of fuel. The tank holds five units. A: So that’s five over two, or two and a half days. That’s pretty good. Are they expensive? B: No. They’re twenty percent cheaper than our last model. I think our next design will be another five percent cheaper. 9 Suggested Answer Test: #119b Please indicate changes since the last progress report. Functionality: The prototypes are more functional than the Book 1 Answer Key last group. The fuel lasts longer. It takes half a day to use one unit. Cost: They are twenty percent cheaper than our last model. Expectations: I predict that the next design will be five percent cheaper than the current model. Unit 14 1 Suggested Answers 1 Visual representations can help people understand data more easily. Tables generally organize written information inti logical categories. They typically include columns and rows. Graphs, like line graphs, bar graphs, and scatter plots, show relationships between different pieces of data. A pie chart displays fractions or percentages of a whole. 2 Most graphs have the same basic features. One variable is measured along the x-axis, while another variable is measured along the y-axis. The relationship between the variables may be represented in a few ways. There may be particular points of data, as in a line graph or scatter plot. Or the data may be shown in blocks, as in a bar graph. A legend provides important information about how to read the graph. 2 Type of Chart Line graph Purpose to show fuel efficiency through each development stage Scatter plot to show results from individual tests to analyze fuel costs over weeks, months, and years to show remaining money Table Pie chart 3 4 1 legend 3 pie chart Parts of a Table Parts of a Graph row column 5 2 line graph x-axis y-axis 4 table Types of Charts bar graph scatter plot Suggested Answer A line graph and a scatter plot both show multiple data points along the x and y axes. However, a line graph includes lines between each point, while a scatter plot just shows the points themselves. A line graph can be used to show improvements and a scatter plot to show individual test results. 6 1F 2T 7 1 bar graph 2 What about 3T 3 some trouble 4 x-axis 5 looks messy 6 scatter plot 8 Suggested Answer A: How is the presentation coming along? B: I just finished the pie chart. It really shows how much money we’re saving. A: What about the bar graph? B: This is useful because it shows the data spread over time. A: How about using a scatter plot? B: That would be helpful because it presents individual results. A: How about a table? That’ll still show the overall improvements. B: That’s a good idea. They really just need to see the numbers. 9 Suggested Answer Hello Mr. Wemberg, I received your request for a project update. The attached materials should give you all the information you need. 1 Pie chart: This shows how much money we’re saving. 2 Bar graph: This shows the data spread over time. 3 Scatter plot: This shows individual results. 4 Table: This shows the overall improvements. Thanks, Clem Nilson Nilson Engineering Unit 15 1 Suggested Answers 1 Simple machines are mechanical devices that improve someone’s ability to apply force or drive movement. They employ basic physics principles to make various tasks easier. 2 Most people use simple machines in everyday life. A doorknob is a simple machine that uses a wheelandaxle mechanism. Devices like crowbars and bottle openers work according to the principle of leverage. Tools with sharpened edges for cutting, such as axes, are examples of wedges. And various types of ramps are used to transport materials to higher levels. Answer Key 11 Book 1 Answer Key 2 Simple Machine Inclined Plane Benefits makes heavy loads easier to elevate Wedge breaks and cuts hard materials Wheel produces smooth, continuous movements makes something seem lighter Lever 3 A fulcrum B lever C pulley D wedge E load F axle 4 1 A leverage 2 A wheel 5 Suggested Answer Someone can increase power by placing certain objects appropriately; for example a lever on a fulcrum can make an object seem lighter. 6 1D 7 1 how leverage works 2 increases the force 3 How much 8 Suggested Answer B simple machines B inclined plane 2A 4 location of the fulcrum 5 picture it 6 real-world example A: I don’t quite get how an inclined plane works. B: An inclined plane makes it easier to move heavy loads. A: But it still has to move against gravity, right? B: That’s true. But a smooth incline offers less resistance than a steep slope. B: I still can’t picture it. A: Maybe a real-world example will help. For instance, roads often wind around mountains, instead of going straight up. B: I see. A car can’t travel vertically. But it has enough power to travel up a gentler slope. 9 Suggested Answer Simple Machines 1 Name a simple machine: Inclined plane 2 How does this machine work? It makes it easier to move heavy loads by reducing the effects of gravity as a smooth incline offers less resistance than a steep slope. 12 Answer Key 3 Describe an example of this machine: Mountain roads are gentle slopes that wind around mountains as cars can’t travel vertically and so the roads don’t go straight up. Audioscripts Unit 1 Unit 5 Engineer: Hi, I’m Ian Moore. I’m here for an interview. Interviewer: It’s nice to meet you, Ian. Tell me about your work experience. Engineer: Well, I worked for Osterbell Incorporated for twelve years. Interviewer: What were your job duties? Engineer: I assessed old engine models. Then I made suggestions to improve them. Interviewer: Did you design any engines? Engineer: Not on my own. I designed new parts for older models. Interviewer: If we hire you, you’ll design new engines as well. Engineer 1: Hey, Jay. I just finished working on that belt drive. Engineer 2: Thanks, Beth. What was wrong? Engineer 1: There was a lot of slippage. I re-tensioned the belt. Engineer 2: I see. It was a v-belt, right? Engineer 1: Yeah. We should replace it soon. We don’t want it to keep slipping on the sheave. Engineer 2: Yeah, we don’t want the engine to break down, either. How long do you think it’ll last? Engineer 1: I’d say no longer than two months. Engineer 2: I’ll put it on the maintenance schedule. Unit 6 Unit 2 Engineer: Vicki, could you do me favor? Assistant: Sure, Paul. What is it? Engineer: Could you please go to the hardware store? I need a couple of bearings. Assistant: Of course. What kind do you need? Engineer: I need two straight roller bearings. Assistant: Okay. Didn’t you break a ball bearing earlier? Engineer: That’s right, I almost forgot. I also need an inner race for a ball bearing. Assistant: Got it. I’ll head out right now. Unit 3 Engineer 1: David, I noticed a problem with your design. This coupling won’t work. Engineer 2: What’s wrong, Kathy? Engineer 1: The input and output shafts aren’t in alignment. Engineer 2: You’re right. It looks like there’s a little bit of offset. Engineer 1: Yeah. It means we can’t use a rigid coupling. It’ll break. Engineer 2: Oh, you’re right. We’ll have to use a flexible coupling instead. What do you recommend? Engineer 1: I think a beam coupling would work best. Engineer 2: I agree. We’ll use that. Unit 4 Engineer 1: How are the plans for the new transmission system? Engineer 2: Pretty good. We need to decide what kind of gear to use. Engineer 1: We should use bevel gears. The shafts meet at right angles. Engineer 2: That makes sense. But I’d like to use helical bears if possible. Engineer 1: Good idea. It’ll reduce noise from the gear teeth. Engineer 2: Exactly. They’ll mesh more smoothly. Engineer 1: I’ll look for beveled helical gears. Owner: Ms. Williams, I received your email about our tools. Engineer: Great. Do you think we can get some of those new screwdrivers? Owner: I wanted to ask you about that. What’s wrong with the old screwdrivers? Engineer: The Phillips screwdrivers we use now don’t fit our new screws. We need slotted screwdrivers. Owner: Oh, I see. We can definitely get the new screwdrivers. Engineer: That’s great to hear. Owner: Is there anything else you need? Engineer: We also need new sets of socket wrenches. Some of the head sizes are missing. Owner: I’ll order those as well. Thanks for your input. Unit 7 Engineer 1: Hi, Wendy. Did you see the new product catalogue? Engineer 2: Yes, I did. And we definitely need some new tools. Engineer 1: Do you have any machine tools in mind? Engineer 2: Well, I suggest that we order a new mill. Engineer 1: Oh, yeah. Some of those CNC mills look really advanced. Engineer 2: Exactly. The new technology would make the process faster. Engineer 1: That’s a great idea. I’ll place the order this afternoon. Unit 8 Engineer: Hey, Lou? Where are those aluminum rods I asked for? Assistant: They’re on the workbench. Engineer: I checked. They are only sixteen centimeters long. Assistant: That’s right. I subtracted two centimeters from the previous measurements, like you asked. Engineer: I wanted you to add two centimeters. Assistant: Oh, I misunderstood. I calculated eighteen centimeters minus two. Answer Key 13 Audioscripts Engineer: That’s okay. Just cut some new rods as soon as you can. Assistant: Of course. So you want the previous measurements plus two, right? Engineer: Right. That’s twenty centimeters each. Unit 9 Engineer: Okay, Raymond. Let’s measure the new components. Assistant: Sure. What do we need to measure? Engineer: Start with the transmission shaft. How long is it? Assistant: Let’s see. It looks like 1.65. Engineer: Really? Wait, is that a metric or imperial measurement? Assistant: Oh, sorry. That’s a metric measurement. It’s 1.65 meters. Engineer: That makes sense. What’s that in feet? Assistant: So 1.65 divided by 0.3 equals 5.5 feet. Unit 10 Engineer: Lisa, do you have the new measurements for the Lynwood project? Assistant: Yes, I just made the conversions. Engineer: Great. So what’s the volume of the fuel tank? Assistant: Let me see. That was 94.5. Engineer: Now that’s a metric measurement, right? Assistant: Yes. It was 25 gallons. That times 3.78 equals about 94.5 liters. Engineer: Okay. And what about the temperature in the tank? Assistant: It was 104 degrees Fahrenheit. So that’s about 40 degrees Celsius. Unit 11 Student 1: I need some help with this physics assignment. Student 2: Sure. What are you supposed to do? Student 1: I need to determine the force. That means I calculate it in newtons, right? Student 2: Yes. Do you remember the formula? Student 1: It’s kilograms times meters squared over seconds squared. Student 2: No, that’s the formula for joules. Those measure energy, not force. Student 1: Really? All these formulas look so similar. Student 2: Yes, a lot of them use the same base units. You want kilograms times meters over seconds squared. Student 1: Wow, that’s confusing. But I think I get it now. Unit 12 Engineer: Hey, Paul? Something’s not right in this equation. Assistant: Really? I checked it twice. Engineer: The energy of this system should be under a thousand joules. Your result came to nearly ten thousand! 14 Answer Key Assistant: Wow, that’s way too high! I wonder what I did wrong. Engineer: Let’s take a look at your formula. Oh, I see what happened. Assistant: What is it? Engineer: The meters are cubed instead of squared. Assistant: I see. So I used the wrong exponent. Engineer: Exactly. You have to be really careful about this. That kind of error could be disastrous. Unit 13 Engineer 1: Do you have the belt-drive test reports ready? Engineer 2: Yes. The prototypes are working better than we expected. Engineer 1: That’s great to hear! What fraction of the set is still running? Engineer 2: Only one failed. That means nine out of ten are still functional. Engineer 1: Wow. Nine tenths is pretty good. Are they efficient? Engineer 2: Yes, they are. They each generate eight percent more power than the previous ones. Engineer 1: Well, the design is really coming along, then. Engineer 2: Definitely. I think our next test will be one hundred percent successful. Unit 14 Engineer: How is that presentation coming along? Assistant: I just finished the bar graph. It really shows how much better the new component is. Engineer: Great. What about the line graph? Assistant: I’m having some trouble. The data points are clustered together. Engineer: Maybe you could spread out the x-axis. Assistant: I tried that. The lines still move up and down a lot. It looks messy. Engineer: How about a scatter plot? That’ll show he overall improvements. Assistant: That’s a good idea. They don’t really need to see all the lines. Engineer: Exactly. Let me see it when you’re finished. Unit 15 Student: Professor Dalton? I don’t quite get how leverage works. Instructor: Well, a lever increases the force of an input. Student: Okay. Let’s say I push on a lever. How much extra force is produced? Instructor: That depends on the location of the fulcrum. If it’s closer to the load, it gives you more power. Student: I still can’t picture it. Instructor: Maybe a real-world example will help. A bottle opener, for instance, relies on leverage. Student: Oh, I see. I can’t open the bottle with my fingers. But I can do it with a lever in the right place. Instructor: Exactly. Book 2 Answer Key Unit 1 Unit 2 1 Suggested Answers 1 Suggested Answers 1 Physicists study matter and how matter moves. They seek to understand the laws that govern the motion of objects in space. They also seek to understand why events happen the way that they do. That is, they want to figure out why things in the universe behave in a certain way. Physicists are involved in many different scientific disciplines. They are interested in atoms and atomic structure. They are also interested in planets and the structure of the universe. 2 Physics relates to everyday life in lots of ways, like the way that objects will fall, how water will flow, and how much force a moving vehicle has when it collides with something. A good grasp of physics and the principles of physics can lead to a better understanding of the world. 1 Electricity is the flow of charged particles. These charged particles are generally electrons. They flow from a negative area to a positive area through a conductor, like a wire. 2 We use electricity for lots of different purposes. Anything that plugs into a wall uses electricity. This includes televisions, microwaves, and computers. Devices with batteries use electricity, too. Devices like cell phones, flashlights, and children’s toys all use electricity. 2 1D 2C 3D 3 A resistance B watt 4 1 DC C charge D volt 2 voltage 3 AC E ohm F ampere G circuit H electron 4 current 5 Suggested Answer - amperes - ohms - volts - watts 6 1T 2F 3F 7 1 electric current 2 charged particles 3 does DC 2 1B 2A 3D 3 A relativistic mechanics B motion C gravity D classical mechanics E energy F matter G quantum mechanics H physics 4 1 quantum field theory 2 speed of light 3 Newton’s Laws 5 Suggested Answer 4 direct current 5 and what is 6 flow of electrons 8 Suggested Answer A: Let’s review one more time. What is an electric current? B: It’s the flow of charged particles through something, right? A: That’s right. Do you remember what AC stands for? B: It stands for alternative current. No, wait, it’s alternating current. A: That’s right. And what is alternating current? B: It’s when the electrons flow in the same direction all the time. A: Are you sure? Think about the name. B: Oh, I was wrong. AC is when the flow changes direction. A: There you go. 9 Suggested Answer 8/20 Please describe two types of electric current. Give an example of each type. 1 Direct current (DC) flows in the same direction all the time. All batteries use DC. 2 Alternating current (AC) switches direction of the flow several times a second. Devices that plug into the wall use AC. Classical mechanics cannot describe the movement of very small particles or very fast-moving particles. Therefore, it does not allow discussion of subatomic structures or the possibility of traveling near the speed of light. 6 1T 2F 3T 7 1 classical mechanics 2 microscopic particles 3 you’re thinking of 4 Quantum mechanics 5 sets of rules 6 the study of 8 Suggested Answer A: Let’s review for the quiz tomorrow. B: Sure, that’s a good idea. I’m pretty fuzzy about all of this. A: I am too. What’s classical mechanics? B: That’s the mechanics of non-microscopic things. A: No, you’re thinking of quantum mechanics. B: You’re right. Classical mechanics focuses on nonmicroscopic things, like engine parts. A: There you go. So what is quantum mechanics? B: Quantum mechanics is the study of atomic and subatomic particles. A: That’s right. 9 Suggested Answer Define each branch in a short sentence. Classical mechanics is the study of the motion and forces of Answer Key 15 Book 2 Answer Key relatively large and slow-moving things. Quantum mechanics is the study of the motion and forces of atomic and subatomic particles. Relativistic mechanics is a branch that applies the theory of relativity to mechanics concepts. Unit 3 1 Suggested Answers 1 A system is a set of processes or procedures that is subject to analysis. Systems can be as complicated as a whole machine or even a network of machines working together. 2 Extensive quantities are factors that can be counted. They change as the amount of a substance changes. On the other hand, intensive quantities cannot be counted. They do not change as the amount of a substance changes. 2 1D 2A 3A 3 A system B final C generation D input E consumption F intensive quantity 4 1 closed system 2 extensive quantity G initial H output 3 universal accounting equation 4 open system 5 Suggested Answer The woman recommends adjusting the temperature in the storeroom. 6 1F 2F 3T 7 1 increasing consumption 2 reduce generation 3 makes sense 4 the temperature 5 guess I’ll install 6 balance out 8 Suggested Answer A: May I ask you a few questions about the email you sent me? B: What can I help you with? A: I want to make sure I understand you. You’re saying that the temperature of the materials is decreasing production? B: That’s right. When they break, it increases consumption and decreases generation. A: That makes sense. So I need to control consumption somehow. B: Correct. The easiest way would be to control the temperature of that storage room. A: I agree. I’m installing a new cooling system today. I hope it helps. A: It will. Everything will balance out once you decrease consumption. 16 Answer Key 9 Suggested Answer Patti, Thanks for your advice. I had some good results. Here’s a breakdown: Changes made: I installed a new cooling system in the storeroom. I was able to keep the materials 10 degrees warmer. Effect on consumption: Because materials weren’t breaking as often, consumption went down. Effect on generation: I have more materials actually being used now, so generation went up. Overall effect on production: Production is back to normal. Thanks again, Greg Unit 4 1 Suggested Answers 1 There are several factors to consider when working with rate processes. One of these is flow rate. This is the volume of liquid that passes through a given area in a certain amount of time. Flux refers to the time required to flow through something. Another important factor is pressure. Pressure is the amount of force applied to an area. 2 Engineers work with rate processes when there are liquids in a system. Water supplies are an example of a rate process. 2 1C 3 2B A pressure B outlet C rate 4 1 diameter 3D D driving force E viscosity F inlet 2 Flow rate G rate process H flux 3 viscosity 5 Suggested Answer Flux and flow rate are related, but refer to different factors. Flow rate is the speed at which something moves. Flux describes how much of something flows through a specific area during a fixed period of time. A system’s overall flow rate determines its flux. 6 1F 2T 7 1 flow rate 2 any idea 3F 3 the viscosity 4 it’s too thick 5 I’m afraid we 6 figure it out 8 Suggested Answer A: How’s the new pump design working? B: We have a few problems. The flow rate is giving us trouble. It’s not fast enough. A: Why do you think that is? B: I think it has something to do with the viscosity of the liquid. A: If it’s too thick it would slow down the flow rate. B: Right. I hope we didn’t test the pump with the wrong Book 2 Answer Key liquid. A: That would be bad. Are there any other problems? B: The pressure keeps dropping at the pump’s outlets. A: We should run some tests to find the problem. A: How do we do that? B: Take the difference between the highest and lowest values. A: The highest value is 500 and the lowest is 450. So the range is 50? B: You got it. Now let’s find the median. Are the numbers in order? A: No. Should I do that? B: Yes, get them in order so we can find the median. 9 Suggested Answer Problems: The flow rate is too slow. The pump also loses pressure at its inlets. Possible explanations: It’s possible that the viscosity of the test liquid is wrong for the pump design. Possible solutions: If we try the pump with different liquids of varying viscosities, we may see a difference in performance. Unit 5 1 Suggested Answers 1 Statistics can provide much useful information. They provide average values out of a set. They help determine how close or far a particular number is to the average outcome of an experiment. They also show how spread out the outcomes are. Statistics can reveal number patterns that are difficult to identify otherwise. They can also show how two factors are related. 2 Scientists use statistics because they make data more understandable. Scientists also use statistics so that they can establish patterns between numbers or outcomes. Statistics can numerically establish a relationship between two or more variables. 2 1C 3 A event B statistics 4 1 A mutually exclusive 2 A sample space 3 A intersection 5 2A 9 Suggested Answer Judith, I got your note. I’ll start on the report, but I’ll need some help. Here’s what I know how to do: I know how to select a random sample of data and put it in numerical order. Here are two things I’ll need help with: I do not know how to calculate the range or the median. Unit 6 1 Suggested Answers 1 There are many different ways to solve problems. Some people solve problems by talking about them. Other people like to draw pictures. Some people like to work alone, while others solve problems better in a group. People have developed different methods and processes of problem solving. Even though one method might not work well for every person, it’s usually best to follow a well-defined process. 2 Problem solving is very important to engineers because it makes up a lot of what they do. Engineers have to solve problems all the time. If they are developing a new kind of technology, they have to decide what materials to use, how it should look, and how it will work. Then, they must analyze different iterations to see which features work best. These decisions involve excellent problem solving skills. 3D C population D median E union F probability G range H sample B independent B outcome B union Suggested Answer 2 3 Analysts should assess random samples because samples should be representative of the whole of the population. 6 1F 7 1 you help me 2 do you need 8 2T 3F 3 never done 4 random sample 5 any experience 6 the range Suggested Answer A: Can you help me with this report? B: Of course. What do you need help with? A: I’m not sure where to start. B: Let’s start by selecting a random sample. A: I already did that. I just don’t have experience analyzing that data. B: We can do something easy first. We’ll calculate the range. 1C 2A A solution B redefine C approach 3D D iterative E problem solving F attack 4 1 procedure 5 Suggested Answer It is beneficial to an employee to use the company’s method of problem solving, because it has been designed especially with engineers in mind. 2F 2 iterations G problem identification H analysis 6 1T 7 1 engine prototype 2 problem with 3 about that 3 synthesis 4 brainstormed 3F 4 identified the problem 5 do next 6 more observations 8 Suggested Answer A: How’s your new engine design coming along? B: I’m having a problem with the idling speed. Answer Key 17 Book 2 Answer Key A: That’s great. Are you doing the feasibility study now? B: Yes, we started earlier this week. A: When will you start working on the detailed designs? B: By early next week. By the meeting on Wednesday I’ll have a few to show. A: Good. The client requested a meeting at the end of the month. A: What are you going to do about that? B: I’ve started to identify the problem. It idles too slowly. A: What’ll you do next? B: I need to analyze the problem further to figure out if it always idles slowly or only under certain conditions. 9 Suggested Answer Step 1: Problem Identification How did you identify the problem? When I realized the engine wasn’t idling properly, I ran some tests to determine the exact problem. The engine is idling at the wrong speed. Specifically, it is idling too slowly. What problem solving steps will you take next? I need to run more tests to determine if the engine always idles slowly or only under certain conditions. 9 Hi Dr. Richardson, Here’s a quick update on the progress of the new design. We finished creating preliminary designs and sketches. We’re working on the feasibility study for the rest of the week. We still need to develop detailed designs and construct models. We’ll be done by the end of the month for the meeting with the client. Thanks, Frankie Jones Unit 7 1 Suggested Answers 1 The design process is intended to help people come up with, plan, and create functional designs. It ensures a methodical approach to creating designs. It also forces people to stay mindful of different constraints and criteria. It helps keep development methods organized and efficient, and it ensures that engineers are attempting designs that are possible and reasonable. That way, they are less likely to waste time and resources on impractical designs. 2 Mechanical engineers design a wide variety of products. They may design actual objects, like engines or machines. They also may design processes. Some mechanical engineers design parts of machines. Others work on heating and cooling systems. 2 1C 3 A criteria B sketch C preliminary design 4 2A 1 identify 3D D constraint E construct F revise 2 narrow down G detailed design H feasibility study 3 assemble 4 verify 5 Suggested Answer The first step in the design process is to identify the problem. The next step is to come up with preliminary designs. Then, a feasibility study narrows down the options. The most promising solutions are then made into detailed designs. 6 1F 2F 3T 7 1 preliminary designs 3 We started it 5 on Wednesday 2 feasibility study 4 detailed designs 6 at the end 8 Suggested Answer A: How’s the design coming along? B: It’s going well. We finished the preliminary designs. 18 Answer Key Suggested Answer Unit 8 1 Suggested Answers 1 Patents are designed to help protect people’s ideas. If a scientist or engineer thinks of something that is useful and can make money, a patent ensures that he or she receives recognition for it, and is able to benefit from the production and sale of the idea. A patent is a legal document that makes it illegal for other people to copy someone else’s idea. Most patents expire after a particular amount of time, so eventually others are able to use the design. 2 People filing patents need to include many details about the product. They need to make sure that the patent includes an accurate description of whatever they want to protect. They also need to include the specifications of the item or device they’re patenting. It’s also a good idea to include drawings of the item, if applicable. Applicants should also include information about the development of the new product or process. 2 1B 2A 3D 3 A witnessed B claims C drawing D specification E milestone F patent duration 4 1 A improvement 2 A technology 3 A utility patent G ornamental H monopoly B patent B intellectual property B design patent 5 Suggested Answer Patents protect any kind of intellectual property. This can include machines, processes, or designs. 6 1T 2F 3F Book 2 Answer Key 7 1 get a chance 2 for a patent 3 I need to 4 worth protecting 5 What happens 6 same improvement 8 Suggested Answer A: Did you look over my papers? B: I did. And I think you need to apply for a patent. A: Really? Why? B: Your new engine is worth protecting. You need to provide detailed information about how to create it, as well as drawings and claims. A: What happens if I don’t file for a patent? B: Nothing happens. But if someone else came up with your design, they could make it and sell it. A: I see. I’ll file right away. 9 Suggested Answer Ms. Lewis, In order to proceed with your patent application, I need some information from you regarding your invention: I need the specifications of the invention. This includes very detailed information about how to create it. I also need drawings and claims. Please get these to me as soon as you can. Thanks, Barry Baker 5 Suggested Answer The researchers tested their hypothesis by creating two groups of coolers. One group had normal hoses and the other used several different sizes. They compared the efficiency levels of the two groups. 6 1T 2F 3F 7 1 the hypothesis 2 more specific 3 test that 4 created two groups 5 the difference 6 still evaluating 8 Suggested Answer A: Tell me about your new experiment. B: We’re investigating how hose size affects cooler efficiency. A: That sounds interesting. What’s your hypothesis? B: Our hypothesis is that larger hoses will increase the efficiency of the coolers. A: How did you test that? B: We created two groups. One had normal-sized hoses and one had larger hoses. And then we compared their efficiencies. We’re still evaluating the results. A: Do you think they’ll support your hypothesis? B: Based on what I’ve seen so far, I expect they will. 9 Suggested Answer Unit 9 1 Suggested Answers 1 The first step in the scientific method is to make an observation. This means that someone notices something in the world that needs to be explained. Once the observation is made, a scientist formulates a hypothesis. This is a reasonable explanation for the observation. Next is an experiment. A scientist then evaluates the results of the experiment. This leads to a conclusion about the hypothesis. 2 A hypothesis is a reasonable explanation for some problem that is based on logic and observation. Scientists develop hypotheses to explain events or processes that they are thinking about or questioning. Once they have a hypothesis, they can begin to test it. A hypothesis must be testable. If not, it’s not a useful tool. If a hypothesis is tested many times with positive results, this is strong evidence in support of the hypothesis. If multiple tests reveal inconsistent or unexpected results, the hypothesis might have to be adjusted. 2 1A 2B 3B 3 A experimental group B testable C evaluate D observation 4 1 experiment 2 problem 3 conclusion 4 scientific method E hypothesis F independent variable G control group H result Problem: Increasing cooler efficiency. Hypothesis: Larger hoses will increase the efficiency of coolers. Independent variable: The size of the hose. Experimental group: A group of coolers with larger-thannormal hoses. Control group: A group of coolers with normal-sized hoses. Conclusion: Based on our results, it appears that our hypothesis was supported. Larger hoses increase cooler efficiency. Unit 10 1 Suggested Answers 1 There are lots of different kinds of construction materials. Stone is a basic material that has been used throughout the history of construction. Wood, or lumber, is another popular material. Metals and plastics are also important materials that are used extensively in modern construction. Plastics are durable and versatile. And metals make up many strong parts of machinery and buildings. Glass is another useful material, which is used to make windows. 2 Steel is a metal alloy that is made of iron, carbon, and other elements. It is an extremely useful building material due to its strength and durability. It also produces precise, reliable tools. Answer Key 19 Book 2 Answer Key 2 1B 2D 3 A steel B rebar 4 1A 2B 3A C alloy D materials science E lumber F ceramics G concrete H polymer 3A 2 1A 5 Suggested Answer - lumber - steel - concrete - glass 6 1T 2F Aluminum, gold, and silver are all very ductile metals. They can be bent very easily without breaking. A brittle material will not change shape very much, if at all, before it breaks. Glass, ceramics, and some kinds of plastics are brittle. If someone tries to bend a brittle material, it will usually break immediately. 3F 7 1 material supplier 2 matter of fact 3 I’ll need concrete 4 any rebar 5 I’ll use it 6 steel 8 Suggested Answer A: I’m submitting an order to the supplier. Do you need anything? B: Yes, I need quite a few things actually. A: What do you need? B: First, I need 100 bags of concrete for the foundation A: All right. What else do you want? B: I also need 150 pieces of lumber for the structure. A: Sure. What about for the interior? B: Of course. I’ll need 100 steel beams for reinforcement. A: Send me an email with specific amounts. 9 Suggested Answer Hi Terry, I need the following materials for the new job: Material Units Needed Purpose Concrete 100 bags of mix for building foundation Lumber 150 pieces for primary structure of building Steel beams 100 (various for concrete lengths) reinforcement Thanks, Del Unit 11 1 Suggested Answers 1 There are many ways to classify materials. One way is to divide them into natural and synthetic. Stone and wood are natural materials. Plastic is synthetic. Another way to classify a material is based on hardness, ductility, brittleness, and malleability. It can also be helpful to classify materials on the basis of their conductivity. 2 Ductility and brittleness are opposites. A ductile material will change its shape substantially before it breaks. 20 Answer Key 2B 3 1 conductor 2 natural 4 1 tensile 2 synthetic 3B 3 hardness 4 luster 5 ductile 6 insulator 3 proportional limit 4 malleable 7 yield strength 8 brittle 5 elastic limit 5 Suggested Answer The material for the project needs to be ductile, hard, and not brittle. It should also be an insulator. 6 1F 2T 3F 7 1 and ductile 2 correct shape 3 under stress 4 yield strength 5 malleable material 6 kind of plastic 8 Suggested Answer A: Let’s talk about materials for the project. B: That sounds good. A: You said you needed something both malleable and strong? B: Yes. I have to create a very specific shape, so it has to be malleable. A: And then once it’s inside the machine it’ll be under stress, right? B: That’s right. What do you think? A: That might be tricky. After all, hardness is a measure of how resistant an object is to being deformed. B: So what do you recommend? A: I recommend using a plastic. You can heat it to create the shape you need. And when it cools it will be hard. 9 Suggested Answer James, Here’s what I understood from your email. Characteristics that you want in the material: You want a material that is malleable, and hard. You want it to have high yield strength and high elastic and proportional limits. Characteristics that you don’t want in the material: You do not want a material that is brittle. You also do not want a material that is a conductor. Characteristics that don’t matter: It does not matter to you if the material has a high luster. It also does not matter if it’s synthetic or natural. If this information is correct, I recommend a plastic that will be malleable when hot and hard when cool. Allison Book 2 Answer Key Vector: A vector is a quantity, like force, that can change in terms of size and direction. Moment: A moment is a measurement of a force’s potential to cause an object to rotate. Magnitude: Magnitude is the size of something. The magnitude of a force is measured in newtons. Unit 12 1 Suggested Answers 1 Force is a vector, so its direction is an important factor. Force is always applied towards something at a particular angle. The magnitude of any vector is also important. In the case of force, magnitude is typically measured in newtons. This relates to the size and strength of the force. A resultant is the cumulative effect of multiple forces on an object, while a moment measures a force’s ability to spin an object. 2 In mechanical engineering, forces can be applied to different types of objects. Some calculations only depend on a single point within an object. These are known as particles. Additional information about the object’s dimensions is important to force calculations. Other calculations require dimensional information since the forces may depend on which part of the object they apply to. These objects are known as rigid bodies. 2 1T 2F 3T 3 1A 2B 3B 4 1 A particle 2 A magnitude 3 A moment Unit 13 1 Suggested Answers 1 Gases and liquids are states of matter, but they have different properties. One of the most obvious differences is that gases disperse throughout a container so that the whole container has the same concentration of gas. Liquid, on the other hand, is heavier than gas. It doesn’t spread to take up the whole container, but remains in a dense form. Gases are lighter than liquids because their molecules are more spread out. Gases can also be compressed to a greater degree than liquids. 2 There are many applications of studying fluid motion. One major application is aerodynamics. Aerodynamics studies how things move through the air. This is important when developing airplanes and spacecraft. Other applications include submarine and boat design. Additionally, these principles are important in designing systems that conduct water, such as pipes and plumbing systems. 4A B vector B resultant B free-body diagram 5 Suggested Answer A free-body diagram is a graphical representation that shows all the forces acting on an object and the direction of each force. 6 1A 2B 7 1 seem unclear 2 you trouble 3 kind of force 4 Moments are 5 with rotation 6 of a force 2 1T 2F 3 A gas B buoyancy 3F C aerodynamics D drag 4 1 Laminar flow 2 fluid E liquid F thrust G wind tunnel H lift 3 turbulent flow 5 Suggested Answer 8 Suggested Answer A: I’m still a bit unclear about the properties of force. B: What are you having trouble with? A: I don’t understand moments. Are they the same as a force? B: No, not exactly. They’re a characteristic of a force. A: I see. And they have something to do with rotation, right? B: That’s right. A moment describes the potential for a force to cause rotation. A: And how do you calculate that? B: You need to know the magnitude of the force, for one thing. Remember what magnitude means? A: Yes, it’s the same as size. And it’s measured in newtons. B: Good job. 9 Suggested Answer Force Worksheet Please define each of the following terms in a complete sentence. The course is divided into two sections. The first half deals with principles and definitions. The second half covers applications of the concepts. 6 1B 2A 7 1 we go over 2 to cover 3 laminar flow 4 the difference 5 quickly and violently 6 smooth 8 Suggested Answer A: Can we go over today’s lecture? B: What do you want to cover? A: I’m confused about laminar flow and turbulent flow. B: Me too. I’m not sure about the difference between the two. A: Well, turbulent sounds like turbulence. And turbulence is rough. So I think turbulent flow is rough. B: So then laminar flow would be smooth. That makes Answer Key 21 Book 2 Answer Key behavior, does it? A: No. More carbon makes the steel stronger, but it reduces malleability. B: We might need more freedom to manipulate the material. sense. Which one is usually faster? A: I think laminar flow is faster. B: Are you sure? I thought turbulent flow was faster. A: Let me check the book. You’re right. Turbulent flow is faster. What else is there? A: There are many different kinds of steel that are stronger 9 Suggested Answer and easier to change the shape of. B: Let’s look into those. Briefly describe the differences between laminar flow and turbulent flow. Laminar flow is uniform or smooth flow. The layers of fluid all move in the same direction. Laminar flow is more likely to be slow-moving. Turbulent flow is rough flow. The fluid moves around an object in an irregular way. Turbulent flow is more likely to be fast-moving. Unit 14 1 Suggested Answers 1 Stress refers to the amount of force applied to an object per unit area of the object. Strain refers to the deformation of an object being subjected to stress. Strain is a result of stress. 2 Stress is important to engineers because they need to ensure that their designs are strong enough to work correctly. If engineers don’t understand how different materials and structures respond to stress, their designs will fail. This can be frustrating, costly, and dangerous. 2 1B 2C 9 Suggested Answer Mr. Rodgers, I got back the material test results. Here are my thoughts. Recommended material: I recommend we use carbon steel. Advantages: It is inexpensive and very strong. Disadvantages: It doesn’t have very good behavior. Other possibilities: Other possibilities include maraging, steel, and tungsten. Please let me know if you would like to talk about this further. Thanks, Sandy Peterson Unit 15 1 Suggested Answers 1 Many careers are available for mechanical engineers. They can work as consultants for the military, government agencies, and private corporations. They can also work as design engineers and actually implement their ideas. Various industries need mechanical engineers to design many different products, including tools, engines, and generators. They can also work as researchers in the field of R&D. Other opportunities exist in public safety and educational fields. 2 Like all engineers, mechanical engineers need to be good problem solvers. They need to think outside the box and address difficult problems in new ways without getting discouraged. Mechanical engineers need to be able to think about many different variables at the same time. They have to have a good understanding of how things move and work. They also need to be able to think creatively and communicate well with others. 3D 3 1 stress 2 plastic behavior 3 Strain 4 internal force 5 fails 6 elastic behavior 7 stretch 4 1 A compression B tension 2 A Elongation B Shear 5 Suggested Answer The woman recommends a particular type of material because it will be used for components which will need to carry substantial loads at varying temperatures. 6 1F 2F 3T 2 7 1 constant strain 2 else is there 3 less expensive 4 either of those 5 different design 6 components fail 8 Suggested Answer A: I think we should use carbon steel. B: What are its advantages? A: It’s inexpensive and very strong. B: That’s good. But it doesn’t have very good elastic 22 Answer Key Career Responsibilities Design Engineer designing machines like engines and generators Researcher designing household and industrial tools supervising operations in manufacturing inspecting machinery of private companies Management Public Safety Book 2 Answer Key 3 A generator B R&D C inspect D technical 4 1 public safety 2 design engineer E consultant F engine 3 researcher 4 management G tool H professor 5 manufacturing 5 Suggested Answer A public safety engineer deals with the health of workers and the general public. He or she might inspect machinery to make sure it’s working properly and will not endanger anyone. 6 1C 2D 7 1 mechanical engineering 2 career options 3 can you tell 4 in R&D 5 Did you like 6 had a lot of 8 Suggested Answer A: I’m not sure what I should do after I graduate. B: It’s a hard decision sometimes. A: I know. What can you tell me about your experience? B: Before I became a professor I worked as a consultant in the manufacturing industry. A: How did you like it? B: It was a good job. I learned a lot. A: Then why did you become a teacher? B: It was always my goal to become a professor. What are your goals? A: I’ve always wanted to design new products and to make plans and solve problems as part of my job. B: Maybe you should work in R&D. 9 Suggested Answer Student: Isaac Templeton Advisor: Jean Finley Interests: The student enjoys designing products. He likes making plans and solving problems. Goals: He hopes to see his designs or creations become real. Possible careers: Design engineer, R&D Answer Key 23 Audioscripts Unit 1 Instructor: Okay Ralph, let’s review one more time. What is an electronic current? Student: It’s when charged particles flow through something, right? Instructor: That’s right. Good job. Now, what does DC stand for? Student: It stands for deep current. No, wait, it’s direct current. Instructor: Yes, and what is direct current? Student: That’s when the flow of electrons switches directions every so often. Instructor: Are you sure? Think about the name. Student: Oh wait, that’s not right. Direct current is when the electrons always flow in the same direction. Instructor: Good. And what is it called when the flow changes direction? Student: That’s AC. And AC stands for alternating current. That’s because the direction of the current alternates, or changes. Instructor: You got it. Can you give an example of DC? Student: Most batteries are DC. The electrons always flow from the negative terminal to the positive. Unit 2 Student 1: Do you want to review for the quiz tomorrow? Student 2: Sure, that’s a good idea. It’s about the different kinds of mechanics, right? Student 1: Yeah, that’s right. I’m still a little confused about the different fields. Student 2: I am, too. We definitely need to study. What’s classical mechanics? Student 1: Classical mechanics is the study of microscopic particles. Student 2: No, you’re thinking of quantum mechanics. Student 1: Oh, that’s right. Quantum mechanics examines atomic and subatomic particles. Student 2: There you go. Different sets of rules apply to tiny particles. So what is classical mechanics, then? Student 1: Now I’m not sure. Is it the study of things you can see? Student 2: Yeah, classical mechanics deals with the movement of large things, like parts of machines. Student 1: That makes sense. What should we cover next? Student 2: Let’s go over quantum field theory. Unit 3 Manager: Hi Ms. Adams. May I ask you a few questions about your email? Engineer: Of course. What can I help you with? Manager: I just want to make sure that I have this right. So the temperature of materials is hurting production? Engineer: Yes, that’s right. The materials are too cold. They 24 Answer Key break easily at cool temperatures. Manager: I hear the broken materials are increasing consumption, is that true? Engineer: Yes. And at the same time, they reduce generation. Manager: That makes sense. So I need to somehow control consumption. Engineer: That’s correct. You need to increase the temperature of that storage room. Manager: I agree. I guess I’ll install better insulation. I hope it helps. Engineer: It will. Once you decrease consumption, everything will balance out. Manager: Thanks so much for your help. Unit 4 Engineer 1: How’s the new pump design working? Engineer 2: We have a few problems to figure out. Engineer 1: What’s going on? Engineer 2: For some reason, it’s not maintaining the correct flow rate. The water movement is not fast enough. Engineer 1: That’s strange. Do you have any idea why that’s happening? Engineer 2: First, I want to check the viscosity of the fluid. Engineer 1: That’s a good idea. If it’s too thick, the pump might not work right. Engineer 2: Exactly. I’m afraid we tested the pump with the wrong kind of liquid. Engineer 1: Hopefully we can figure it out. Is that the only problem we’re having? Engineer 1: No. The pressure at the inlets is too low. Not enough material is passing through. Engineer 2: Could that be related to the fluid viscosity, too? Engineer 1: It might be. We’re running tests now to check. Unit 5 Assistant: Hi Judith. Can you help me with this statistical report? Engineer: Sure, Randy. What do you need help with? Assistant: Well, I’ve never done any of this before. I don’t even know where to start. Engineer: Okay. Let’s start by selecting a random sample. Assistant: Oh, actually, I already compiled the data. I guess I just don’t have any experience manipulating the numbers. Engineer: We’ll do something easy first. Let’s figure out the range. Assistant: What’s the range? Engineer: It’s the difference between the highest and lowest values. So first, find the highest value. Assistant: All right. It’s 550. And the lowest is 330. So the range would be 220? Engineer: That’s right. Now let’s find the median. Are the numbers in order from largest to smallest?. Audioscripts Assistant: No they aren’t. Should I do that first? Engineer: Yes, get them in order. Then we can find the median. Unit 6 Engineer 1: Hi Stanley. How does your new engine prototype look? Engineer 2: I’m having a problem with idling speed. Engineer 1: What have you done about that? Engineer 2: I identified the problem. The engine idles too fast. Engineer 1: That’s a good start. What will you do next? Engineer 2: I need to make some more observations. Then I can make a better analysis of the problem. Engineer 1: Good idea. Is the idling speed always off? Or is it only off under certain circumstances? Engineer 2: That’s something I should find out. It’s the only way to determine what’s causing it. Engineer 1: Of course. Well, let me know when you finish your observations. Engineer 2: Yeah, I could use your help to brainstorm new solutions. Engineer 1: Sure. I’ll help you develop a new iteration of the prototype. Unit 7 Owner: How is your design coming along? Engineer: It’s going well. We developed quite a few preliminary designs and sketches. Owner: Great. So are you working on the feasibility study now? Engineer: That’s right. We started it this week. Owner: So you’re ahead of schedule? That’s great! When will you start working on the detailed designs? Engineer: By early next week. I’ll bring them to our meeting on Wednesday. Owner: That sounds good. The client wants to meet with us at the end of the month. Engineer: We’ll definitely have a prototype by then. Owner: Can you get it done a few days earlier? I’d like to evaluate it before we meet with the client. Engineer: That shouldn’t be a problem. We’ll have plenty of time. Owner: I’m glad to hear it. I look forward to seeing the models. same improvement. Then that person could sell it. Engineer: But if I file for the patent, no one can do that? Attorney: Right. You’ll have a monopoly on that product. Engineer: But there is no product yet. It’s still in development. Attorney: That doesn’t matter. You can still get a patent. Engineer: Really? How does that work? Attorney: The design is your intellectual property. Even though it’s not produced yet, you still own it. Engineer: In that case, I’ll file right away. Unit 9 Engineer 1: Hey, I heard you just finished an experiment. What was it about? Engineer 2: It tested cooler efficiency. Engineer 1: Oh yeah? What did you discover? Engineer 2: We thought there was a link between hose size and cooler efficiency. Engineer 1: So was that the hypothesis you tested? Engineer 2: It’s a little more specific. Our hypothesis is that smaller hoses increase efficiency. Engineer 1: How’d you test that? Engineer 2: We created two groups of coolers. One group had normal hoses and the other had smaller ones. Engineer 1: Oh, and then you measured the difference in their efficiency levels? Engineer 2: That’s right. The testing is finished, but we’re still evaluating the results. Engineer 1: Do you think your conclusion will support your hypothesis? Engineer 2: Actually, no. The results so far are pretty surprising. Unit 10 Owner: I’m placing an order with our materials supplier. Do you need anything? Engineer: As a matter of fact, I do. I’m starting on the Nelson project next week. Owner: Oh, that’s a big one. What do you need? Engineer: To start, I’ll need concrete for the foundation. Owner: Sure. Will you need any rebar? Engineer: Definitely. I’ll use it to reinforce the concrete. Owner: No problem. What else should I order? Engineer: Well, the client wants to use steel instead of lumber. Owner: Really? So are you going to use steel? Unit 8 Engineer: Yes, that’s what I’m planning to do. I’ll need a large Engineer: Thanks for meeting with me. Did you get a chance to quantity to get started. look over the papers I sent? Owner: Wow. Does the client know how expensive that will be? Attorney: Yes. Did you file for a patent yet? Engineer: Yes. I gave him a cost estimate, and he still wants to Engineer: No, I’ve never filed for a patent before. Do you think I use steel. need to? Owner: Okay. Well, we should place this order today. Send me Attorney: Yes. Your improvement to the four-stroke engine is an email with all the specifics. worth protecting. Engineer: Good idea. I’ll do that right away. Engineer: What happens if I don’t apply for this patent? Attorney: Probably nothing. But someone else could think of the Answer Key 25 Audioscripts Unit 11 Engineer 1: Hello, Heidi? I just got your email. Do you have a minute to talk? Engineer 2: Of course. Thanks for calling. I just can’t find the right material for this project. Engineer 1: You want something both hard and ductile, right? Engineer 2: Yes. I need to form it into the correct shape. But it needs to stay hard while the machine operates. Engineer 1: That might be a little tricky. It’ll be under stress in the machine, right? Engineer 2: That’s right. So it needs a high yield strength. Engineer 1: That’s hard to find in a malleable material. After all, malleability measures how well something bends without breaking. Engineer 2: Yeah, I know. So do you have any ideas? Engineer 1: I would try some kind of plastic. It will be malleable when you heat it. Engineer 2: Oh, right. And when it’s the correct shape, I can let it cool. Engineer 1: Exactly. Then it’ll remain hard and hold the correct shape. Student 2: Let me check my notes. Oh, I think I get it now. Student 1: What do your notes say? Student 2: In turbulent flow, the fluid layers all move in different directions. Student 1: Oh, right. So they’re mixing with each other. That’s what makes it so rough. Student 2: Exactly. And in laminar flow, all the fluid flows in the same direction. Unit 14 Engineer: Mr. Rodgers? I have the results from the materials tests. Owner: Great. So, what material do you recommend? Engineer: Maraging steel performed the best. I think it will produce the strongest machine components. Owner: What are its advantages? Engineer: It’s very durable. It can withstand fairly high tension. Owner: That’s one of the main requirements for this project, isn’t it? Engineer: Yes. The machine components will be under constant strain. Owner: It’s really expensive, though. I’m not sure if we can afford Unit 12 that. What else is there? Engineer: Carbon steel and cast iron are less expensive. But Instructor: Are you ready for the quiz tomorrow? they don’t handle stress as well. Student: The properties of force still seem unclear to me. Can Owner: Would either of those work for our purposes? we go over a few things? Engineer: I’m not sure. They would require a different design. Instructor: Sure. What’s giving you trouble? Owner: Well, if the components fail, that will cost even more. Student: I don’t understand moments. Are they a kind of force? Let’s just go with the maraging steel. Instructor: Not exactly. Moments are a component of a force. Student: They have to do with rotation, right? Instructor: Right. Moments describe the ability of a force to Unit 15 rotate something. Student: Dr. Owens, may I ask you a few questions? Student: So how do you figure that out? Instructor: Of course, Isaac. What can I help you with? Instructor: You have to look at a couple things. One is the Student: I definitely want to work in mechanical engineering. But magnitude of the force. Do you remember what that is? I’m not sure what to do after I get my degree. Student: That’s its size. It’s measured in newtons, I think. Instructor: There are so many career options for mechanical Instructor: You got it. You also have to know the direction of the engineers. It’s tough to make a decision. force. Student: It sure is. What can you tell me about your experience? Student: Oh, and you can usually get that from the free body Instructor: I started my career with a large machinery company. I diagram. I think I’m getting it. worked in R&D. Student: That sounds really interesting. Did you like it? Instructor: Yes, I really enjoyed it. I had a lot of creative Unit 13 freedom. Student 1: Hey, Rachel. Can we go over some points from the Student: Why did you become a professor? Instructor: I always wanted to work with students. What are your lecture? goals? Student 2: Sure Brad. What did you want to cover? Student: I want to see my designs in use. That’s my biggest Student 1: That part about laminar flow and turbulent flow goal. confused me. Instructor: Maybe you should consider working as a design Student 2: Me too. I’m not quite sure what the difference is. engineer. Student 1: Well, “turbulent” means that it’s moving quickly and violently. Student 2: That’s right. And laminar flow is smooth. Student 1: Yeah, I know all that. But what makes each type behave in a certain way? 26 Answer Key Book 3 Answer Key 9 Suggested Answer Unit 1 Kinetic energy is energy in motion, whereas potential energy is any stored energy. Potential energy could include gravitational or elastic potential energy. The differences can be illustrated in the following example; a ball sitting at the edge of a cliff has gravitational potential energy but once you actually drop it, it has kinetic energy. 1 Suggested Answers 1 The most important type of energy is mechanical energy, which is actually a combination of many different types of energy within a mechanical system. Mechanical energy is the combined total of potential and kinetic energy. Gravitational potential energy, electric potential energy, and elastic potential energy all contribute to calculating Unit 2 mechanical energy. Thermal energy is a type of kinetic energy, and therefore also counts towards the total 1 Suggested Answers mechanical energy in a system. 1 There are three methods for transmitting heat. The first 2 Potential energy is different from other forms of energy. method is conduction, which is heat transfer through Potential energy is energy that is stored in an object, but direct contact. The second method is convection, which is is not currently in use or in motion. For instance, heat transfer through molecular currents in a fluid. The gravitational potential energy is potential energy that is third method is radiation, in which heat is transmitted calculated relative to the object’s elevation. Elastic through waves of particles. potential energy exists in objects that are stretched or 2 Thermodynamics is very important in mechanical bent, and the energy is released when the object springs engineering. It is the study of heat energy, and focuses on back into shape. the use of heat energy for performing work. Historically, 2 1T 2F thermodynamics was vital to the development of steam powered machinery. The laws of thermodynamics continue to guide engineers today in creating efficient heating and cooling systems, as well as harnessing thermal energy for power. 3F 3 A kinetic energy B work C elastic potential energy D power 4 1 A chemical energy 2 A conserve E gravitational potential energy F energy efficiency G thermal energy H energy quality B Mechanical energy B convert 2 1C 3 A BTU B thermodynamics C heat D laws of thermodynamics 5 Suggested Answer Elastic potential energy is stored when an object is stretched, bent, or compressed. It is released as kinetic energy when the object springs back to shape. 6 1C 2B 3B 4 1 A combustion B radiation E specific heat F burn G thermal conductivity 2 A Convection B conduction 2A 5 Suggested Answer 7 1 mechanical energy 2 kinetic energy 3 in motion 4 elastic potential energy 5 count towards 6 Thermal energy A material’s ability to transfer heat by conduction is affected by its thermal conductivity. 6 1F 2T 3T 8 Suggested Answer 7 1 on the quiz tomorrow 4 specific heat A: Do you have a minute? I don’t think I understand 2 go over 5 thermal conductivity gravitational potential energy. 3 conduction 6 convection B: It’s the stored energy in an object relative to its elevation. A: I see. I thought it was the energy of objects that are falling. 8 Suggested Answer B: If the object is falling, that’s kinetic energy. A: Should we go over heat transfer? A: Could you give me an example? B: That’s a good idea. Do you remember what radiation is? B: Think of it like this: If there’s a ball sitting at the edge of a A: Radiation is the transmission of heat through molecular cliff, it has gravitational potential energy. Once you currents. actually drop it, it has kinetic energy. B: You’re thinking of convection. Radiation is heat A: What about a roller coaster at the top of a curve? Does that transmission through particle waves. count? A: That’s right. I always get those confused. B: Yes, it does. But once it starts to roll down the slope, it has B: I have a question. Do the laws of thermodynamics define kinetic energy. heat as energy transfer? A: I’m pretty sure they do. Answer Key 27 Book 3 Answer Key 9 Suggested Answer 8 Suggested Answer A: We’re still having problems with that engine. B: Do you mean the gasoline engine? A: Yes. We resolved the problem with the spark plugs. But unfortunately, now the engine is leaking oil. B: Hmm. That could be serious. Let’s check the sump just to be safe. A: If it is the sump, it’s an easy fix. B: What if that’s not it? Should we check the valves, too? A: I didn’t think of that. That’s a good idea. Heat and Thermodynamics Heat can be transferred in one of three ways: conduction, convection, and radiation. Radiation is heat transmission through electromagnetic waves. Convection is heat transmission through molecular currents. These seem similar, but thanks to my study partner, I understand the difference now. Note: Combustion is NOT a method of heat transfer. Don’t get these things confused. 9 Suggested Answer Unit 3 1 Suggested Answers To: Design Engineers From: Kit Baker 1 Combustion engines use the energy from fuel combustion As many of you know, we’ve had a recurring problem with the to generate propulsion. Combustion occurs inside multiple gasoline engine. At first we suspected faulty spark plugs and cylinders and must be carefully synchronized. Each simply replaced them. After this, unfortunately the engine cylinder contains a piston, which is connected to the started leaking oil. We realized that the problem could end up crankshaft by a connecting rod. When combustion occurs being very serious, so we decided to check the sump and the inside the cylinder, the piston is forced downward, valves. transferring energy to the crankshaft. The engine block houses the cylinders, and the crankcase houses the crankshaft, protecting it from the interference of other Unit 4 parts. The engine head covers the cylinders and holds the 1 Suggested Answers spark plugs. 1 A two-stroke engine completes a power cycle in two 2 Gasoline engines and diesel engines work in slightly strokes of the piston and one full revolution of the different ways. Since gasoline and diesel fuel have crankshaft. After fuel and air enter the chamber, the different viscosities, they require different circumstances piston rises to compress the mixture. The spark plug fires to combust. In a gasoline engine, fuel and air are mixed and ignites the compressed fuel and air, forcing the piston together and enter the combustion chamber down. More fuel and air enter the chamber while the simultaneously. A spark plug uses electricity to generate a exhaust from the previous combustion exits. Because of spark that ignites the fuel. In a diesel engine, fuel is this design, twostroke engines generate a lot of power injected into the cylinder by a fuel injection pump. relative to their weight. However, sometimes exhaust Pressure alone ignites the fuel. However, since diesel remains in the chamber after combustion, or some fuel becomes more viscous at low temperatures, the engine escapes with the exhaust. must be heated to a minimum operating temperature in 2 Two-stroke engines require two-stroke oil in order to order to work. Glow plugs help preheat the engine in cold function properly. Since two-stroke engines do not have a weather. sump or other oil reservoir, they have to be lubricated differently than other engines. Tw-stroke oil is mixed 2 1T 2T 3F directly into the fuel, and lubricates the cylinders when fuel is drawn in. It is extremely important to have the 3 A connecting rod D cylinder G engine block correct fuel-to-oil ratio for a particular engine. If there is B diesel E fuel injection pump H crankshaft too much oil, friction will cause the engine to overheat C sump F valve and burn out. 4 1 piston 2 spark plug 3 piston ring 4 crankcase 5 head 6 combustion chamber 7 glow plug 5 Suggested Answer Without glow plugs, diesel engines would not start in cold weather. 6 1A 28 Answer Key Action 3 connecting rod 4 unfortunately Purpose Following fueling procedures to ensure that fuel does not ignite during fueling Causing the spark plug to to ignite the fuel and air mixture fire Forcing the piston downward to turn the crankshaft Lubricating the engine 2D 7 1 gasoline 2 diesel engine 2 5 combustion chamber 3 A exhaust 6 piston B cycle to prevent the engine from burning out C mix D fuel-to-oil ratio E revolution F fuel G two-stroke oil H compress Book 2 Answer Key 4 1 burn out 2 fire 3 inlet chamber. This means that there will not be adequate pressure in the chamber for combustion. It also means that highly flammable gases are leaking from the engines, which could potentially be very dangerous. Exhaust could also leak from the combustion chamber as well, possibly becoming trapped elsewhere rather than being properly vented. 4 two-stroke engine 5 Suggested Answer For safety reasons, the vehicle should be fueled by adults only. Gasoline is highly volatile and it is dangerous for children to handle. 1D 6 7 2A 1 exhaust 2 two-stroke oil 8 3 mixed in 4 two-stroke engine 5 fuel-to-oil ratio 6 burn out Suggested Answer 2 1T 2T 3F 3 A intake valve B exhaust valve C pressure D head gasket G cylinder E ignite head F four-stroke engine A: We’re going to start designing a motorcycle engine. 4 1 A intake stroke B exhaust stroke 2 A compression stroke B power stroke B: Sounds interesting. I never worked on a motorcycle engine before. 5 Suggested Answer A: Have you worked on any kind of two-stroke engine? Pressure builds up during the compression stroke because a B: Only once. I remember that it took a special type of oil. head gasket seals the chamber and so the fuel mixture cannot A: Right. And the two-stroke oil gets mixed in with the fuel. escape, building pressure inside the chamber. B: I’m guessing that’s the only form of lubrication for the cylinders? 2C A: Right. Now remember, it’s very important to have the right 6 1 A fuel-to-oil ratio. 7 1 take a look 4 checked the cylinder B: It sounds like that could lead to serious problems 2 generating enough power 5 head gasket otherwise. I’ll remember that. 3 I was thinking 6 did you look at 9 Suggested Answer Alice, Here are the specifications for the motorcycle engine project that we are working on. We will start the project next week, but for now, take a look over the plans. The motorcycle will have a fairly standard two-stroke engine. This type of engine uses a special type of oil. The two-stroke oil gets mixed with the fuel. It is the only type of lubrication used for the cylinders. Don’t forget that it is essential to make sure that you see the right fuel-to-oil ratio, or else there will be serious problems to the engine. Let me know if you have any questions. Steve Unit 5 1 Suggested Answers 1 8 Suggested Answer A: Did you take a look at that engine? B: There’s definitely an issue with cylinder four. A: Did you do an inspection? B: I checked the head gasket. I thought it might be damaged. But nothing’s wrong with it. A: I was thinking maybe there was an issue with the intake valve. B: I didn’t look at that yet. A: I’ll take a look at the intake valve and let you know what I find. B: Maybe you should check the exhaust valve, too. A: That’s a good idea. 9 Suggested Answer Date: 4/14 We encountered a problem with a four-stroke engine yesterday. Cylinder four is definitely in trouble. We did an inspection and checked the head gasket, thinking we would find it damaged but nothing was wrong. We would like to explore the possibility that the problem is with the intake valve or the exhaust valve. Since the problem has not yet been resolved, we will inspect these two valves and let you know what we find. A four-stroke engine uses four piston strokes to generate power. The intake stroke draws fuel and air into the combustion chamber. The compression stroke compresses the fuel and air. At the top of the compression stroke, the fuel ignites. The force from the combustion forces the piston downward, generating power. This is called the power stroke. On the exhaust stroke, the exhaust valve opens and the rising piston pushes exhaust out of the combustion chamber. Unit 6 2 It is extremely important that engine cylinders are gastight. There are a number of potential consequences if the 1 Suggested Answers 1 Degrees and radians are both measurements of angles. head gasket is out of place or if the cylinder is damaged. However, they represent angles somewhat differently. In First, fuel and air may escape from the combustion Answer Key 29 Book 3 Answer Key a system that uses degrees, a circle is assumed to have the manipulators can rotate. Currently, their movements are 360º. Thus, each degree is 1/360 of a complete circle. A very limited. By improving the arc length of their potential radian is the angle that results from an arc length that movements, you would allow the machine to cover a larger equals the circle’s radius. Although they are determined area. As a result, you could use fewer machines. differently, their relationship can be represented by a Second, I recommend increasing the speed at which the machines rotate. This will allow them to complete more work formula. One radian is equal to 180/π degrees. in the same amount of time. This is especially important if you 2 There are two ways to describe the speed of rotational accept my first suggestion. If the radius and arc length motion. One way is to describe it as distance over time. change, you’ll have to account for the change in the angular To describe it this way, someone must find the arc length velocity as well. traveled by a point on the object’s surface. In this way, the Sincerely, speed is defined as the arc length over the traveling time. Erin Anderson, Mechanical Engineer The other way to describe the rotational speed is in revolutions per unit of time. To measure this, someone needs to count how many times the object completes a Unit 7 rotation in a given amount of time. 1 Suggested Answers 2 1T 2F 3 A angle θ B revolution 1 A gearset’s pitch is important because it provides information about the functionality of the gearset. It indicates how far apart the teeth of a gear are. 2 Shift forks move a gear along a shaft. The gear can then come into contact with other gears of different sizes. 3T C RPS D pivot point 4 1 A center of rotation 2 A degree E RPM F rotational motion G radian H radius B angular velocity B arc length 2 1F 3 A gearset B speed 5 Suggested Answer RPM is the number of revolutions that an object completes in a minute, whereas RPS is the number of revolutions per 4 second. 6 1B 2T 3F C shift fork D slip 1 A torque ratio 2 A pitch circle 3 A pitch radius E pitch F frictional loss G grind H torque B velocity ratio B output torque B input torque 2D 5 Suggested Answer 7 1 rotational motion 2 machines’ RPM 3 they’re pretty slow 4 Are you sure 5 angular velocity 6 just to cover The velocity ratio and the torque ratio are inversely proportional, which means that, oppositely to the velocity ratio, the torque ratio equals output torque over input torque. 8 Suggested Answer 6 1T 2T 3F A: Your manufacturing line’s painting machines are pretty slow right now. I think you should increase the speed of 7 1 review pitch 3 the same point 5 don’t fit together their rotational motion. 2 a gear’s teeth 4 in a gearset 6 pitch circle B: You mean adjust their angular velocity? A: Yes. You can probably increase their speed safely. B: That will allow them to work more in the same amount of 8 Suggested Answer time. A: I’m worried about this exam. A: Also, your machines have a limited range of motion. They B: I’m a little worried, too. Do you want to study? can only rotate a short distance. A: Sure. Can we talk about pitch first? B: Would you recommend increasing it? B: Good idea. So, what is pitch? A: Yes. Increasing their potential motion’s arc length will A: I think it’s the distance between two teeth on a gear. improve their reach. B: Right. More specifically, it’s the distance between a point B: What effect will that have? on one tooth and the same point on the next tooth. A: Since each machine will be able to cover more area, you’ll A: I remember now. So what’s the velocity ratio? be able to use fewer of them. B: That’s the relationship between the number of teeth on each gear. 9 Suggested Answer A: And that’s the opposite of the torque ratio. Dear Mr. Smith, B: Right. They’re inversely proportional. Do you remember I have a couple of suggestions for improving your factory’s the formula? serial robots. First, I recommend increasing the distance that A: I think so. Torque ratio is output torque over input torque. 30 Answer Key Book 3 Answer Key B: What’s the problem? A: It looks like one of the idler gears is worn. The teeth aren’t meshing correctly. B: That sounds like a problem. What do we need to do to fix it? A: I suggest casting the idler gear out of a stronger material. B: How long will it take to change the prototype? A: It’ll take at least a week to replace the gear and run the tests. B: I’ll tell the production staff to expect a delay. B: You know more than you thought you did. 9 Suggested Answer Terms that will be on the midterm exam: Pitch: A gear’s pitch is how far apart a point on one tooth is from the point on the next tooth. Two gears in a gearset must have the same pitch in order to fit together properly. Torque ratio: A torque ratio in inversely proportional to the velocity ratio. It equals the output torque divided by the input torque. 9 Suggested Answer Unit 8 Date: November 20 Engineer: Peter Smith Last week, my team and I encountered a problem with our new compound geartrain project. The idler gears were worn and the teeth weren’t meshing correctly. We suggested casting the idler gear out of a stronger material. It took a week to replace the gear and run the tests. The geartrain is now operating smoothly and it is safe to begin production. 1 Suggested Answers 1 There are several different types of geartrains. Simple geartrains are serial connections of three or more gears. In a simple geartrain, each shaft has only one gear. The second type of geartrain is a compound geartrain. In a compound geartrain, a shaft may have more than one gear, each with a different number of teeth. Compound geartrains can transfer power across different planes. Planetary geatrains are some of the most complex, Unit 9 requiring specialized gears and support hardware. 2 Planetary geartrains are some of the most complex types 1 Suggested Answers of geartrains. Planetary geartrains have a sun gear in the 1 Engineers use CAD to create drawings and models. center. Multiple planet gears travel around the sun gear, Sometimes a technical drawing is necessary when driven by torque from the carrier or spider. The planet presenting a design to a client. Or engineers might make gears transfer rotation to the sun gear, which creates drawings or models to identify any problems with the rotation in the output shaft. The geartrain is contained by design before much more work is done. Creating a an inside gear called the ring gear. The ring gear in a computer model of an object allows designers to stimulate planetary geartrain is usually fixed. A balanced geartrain the way that something will function. can reduce wear on the individual gears by distributing the 2 CAD has many advantages over traditional drafting. For forces more evenly. one, designing and changing models is faster and easier. 2 1D 2A 3 A serial B compound geartrain C spider 4 1 direction 2 idler gear D sun gear E mesh point F simple geartrain 3 ring gear 4 planetary geartrain G planet gear 5 carrier 5 Suggested Answer Customers should verify the necessary direction of output rotation because the direction of rotation reverses at every mesh point. If they do not verify this information, the geartrain may be incompatible with the machine. 6 1F 2T Using CAD also allows drafters to create more complex models of their designs. These models do not require substantial time and resources, so designers have the freedom to explore more possibilities. Some programs also allow designers to test their designs. 3B 1D 2C 3 A 2-D B B-rep 4 1 IGES 2 drafting 3D C CAD D PDES E 3-D F CSG 3 technical drawing 4 exploded views G model H photorealistic rendering 5 manifold model 6 non-manifold model 5 Suggested Answer 3T 7 1 planetary geartrain 2 spider 3 pretty bad 2 4 too much friction 5 planet gears 6 How long will it take 8 Suggested Answer A: We ran into an issue with the new compound geartrain. The new program can create exploded views, manifold models, and non-manifold models. Also, it is compatible with IGES and PDES. 6 1T 2F 3T 7 1 make a model 2 we have now 3 much easier to 5 can you create 5 manifold model 6 level of detail Answer Key 31 Book 3 Answer Key 8 Suggested Answer A: A new CAD program would help me out with my latest project. B: What are you working on? A: I’m designing a new engine and I need to make an exploded view. B: Can’t our current program do that? A: No, unfortunately it can’t. But the new one can. B: I see. What else does the new program do? A: It creates B-reps, manifold models, and photorealistic renderings. B: That’s impressive. What kind of files does it support? A: It can read and create IGES and PDES files. B: You convinced me. I’ll order it right away. 9 Suggested Answer 2 1C 2D 3 A concurrent engineering B packaging C material selection D planned obsolescence 4 1 A Bottom-up design 2 A Systems engineering E top-down design F design strategy G product management B lifecycle assessment B manufacturing process management 5 Suggested Answer When products are created with planned obsolescence in mind, their useful life is very short. Material life extension ensures that the parts can be reused or recycled, reducing waste and production costs. Many companies now understand the financial and ecological value of recycling materials. Hi team, I am excited to announce that we will be using new CAD software next month. It is a great program with lots of new 6 1T 2F 3T features. The firm’s new CAD software program is different from our old program, as it allows you to make an exploded 7 1 lifecycle assessment 4 material selection view of your design, something that isn’t possible with the old 2 packaging 5 I’m afraid software. The new program can also create B-reps, manifold 3 material intensiveness 6 systems engineering models and photorealistic renderings. This new software will be of great benefit to the company because we will be able to 8 Suggested Answer use it to produce much more sophisticated models to impress A: I think we should improve the product lifecycle our clients with. management for the new drill press. Tanya B: There’s always room for improvement. What area do you want to work on? Unit 10 A: The team and I are concerned about our systems 1 Suggested Answers engineering. 1 There are several different areas of product lifecycle B: That makes sense. We could stand to coordinate better to management. The first is systems engineering. Systems meet consumer needs. engineering coordinates all of the different areas of A: Exactly. Personally, I think we should also improve our product lifecycle management while also focusing on product data management. consumer needs. Product lifecycle management involves B: You’re right. We’re not keeping good records. both product development and product marketing. A: Yes. But I’m concerned that we might not be able to Product management is primarily concerned with planning convince the rest of the team. and forecasting a product’s market life. Manufacturing B: The trouble is getting everyone to agree. process management deals with how the product will be manufactured, including what technology will be used. 9 Suggested Answer Product data management deals with collecting and The drill press project 1065B would benefit from better organizing product data during all stages of a product’s product lifecycle management. In particular, we should lifecycle. improve our systems engineering by coordinating better to 2 Product lifecycle management is an essential part of a meet consumer needs. I suggest that we should improve our product’s development and overall life. Effective product product data management, as currently we are not keeping lifecycle management allows engineers and developers to good records. This can become our most valuable resource. set priorities and forecast a product’s lifecycle during the Both departments must work together towards our common design process. Engineers can assess factors such as a goal. product’s environmental impact, from material selection to packaging and the end of the product’s useful life. Unit 11 Depending on the company’s environmental concerns, they can choose either planned obsolescence or product 1 Suggested Answers 1 There are many different technologies that contribute to lifecycle extension. In the case of planned obsolescence, robotics and automation. Some technologies affect the they may choose to make material life extension a priority. 32 Answer Key Book 3 Answer Key way robots move. If a robot is powered by a hydraulic machinery, it uses the movement of fluid to generate motion. By contrast, pneumatic robots use pressurized gas to control motion. Some devices, like pendants and enabling devices, are used to program robots or control them directly. 2 Most serial robots have virtually the same components. An actuator controls the moving parts of a serial robot. The arm-like structure of the robot is called a manipulator, and the manipulator has multiple joints that give it different degrees of freedom. At the end of the manipulator arm is an end-effector, which interacts with the payload. 2 Technology Six-Joint Serial Robots Seven-Joint Redundant Manipulator Hydraulic and Pneumatic Robots Four-Joint Robots 3 4 Unit 12 1 Suggested Answers 1 There are several different techniques for structural analysis. The first is mechanics of materials, also called strength of materials. The mechanics of materials approach to structural analysis concerns the way materials behave under stress and different loads. The elasticity theory approach examines how materials deform elastically when loads are applied. These first two methods are useful for simple analysis and most mechanics of materials and elasticity theory problems can be solved by hand. The finite element method is a mathematical approach that is highly dependent on computers. FEM analysis can solve very complex problems and is useful for analyzing complex systems. 2 Some people might think that structural analysis only applies to civil engineering, but it is very important to mechanical engineering as well. Many large machines are considered nonbuilding structures by engineering standards. Construction equipment like cranes and carnival rides such as roller coasters and Ferris wheels are considered nonbuilding structures. Structural analysis helps engineers assess how machines will behave when loads are applied. Complex analysis approaches like FEM are also useful for analyzing machines that are not structures. Work Performed improve dexterity of robotic end-effectors designed a robot that operates in multiple configurations compared performance between types tested robots under varying payloads and repaired robots A manipulator D joint G payload B hydraulic C pneumatic E robotics F end-effector H automation I actuator 1 serial robot 2 pendant was for this position by Keven Schwartz in the robotics department. I have twelve years of experience working with serial robots. In my previous position with Buena Vista Industries, I worked with actuators for serial robots. I’m interested in learning more about teach pendants and pneumatic machinery. I believe that my combined background in mechanical engineering and software programming makes me an ideal candidate for this position. I look forward to hearing from you soon. Francisca Stewart 3 enabling device 4 dexterity 5 flow line 6 work envelope 5 Suggested Answer The engineer assisted in developing a seven-joint redundant manipulator robot. She has also designed an end-effector that operates on electro-adhesive properties. 6 1F 2T 7 1 robotics 2 automation 3T 3 serial robots 4 flow lines 5 six-joint manipulators 6 pendants 8 Suggested Answer A: Tell me about your engineering experience. B: I’ve been a robotics engineer for twelve years. A: What kind of automation have you worked with? B: Most of my experience is with actuators for serial robots. A: Have you done any work with teach pendants? B: No, but I’ve always been interested in learning about it. A: What is the most challenging aspect of robotics for you? B: I’d have to say working with pneumatic machinery. It’s frustrating for me. 9 Suggested Answer Dear Sir or Madam, I’m applying for your available robotics engineer position. I 2 1T 2F 3F 3 A structural load D nonbuilding structure B element E support C catenary F structural analysis 4 OneDimensional arch beam column TwoDimensional plate shell Analysis Approach mechanics of materials elasticity theory finite element method 5 Suggested Answer It is a prerequisite that students have an understanding of mechanics of materials, in order to take the course. This is important because students will learn to assess a structure’s ability to support loads. Answer Key 33 Book 3 Answer Key 6 1C 7 2B 1 structural analysis 2 nonbuilding structures 3 support 3 A creep B fatigue C failure analysis D failure rate E fracture 4 1 A ductile failure 2 A Corrosion 3 A macroscopic failure 4 structural loads 5 mechanics of materials 6 how much weight 8 Suggested Answer A: I’m a mechanical engineering student. Why do I need to learn structural analysis? B: Plenty of machines are nonbuilding structures. A: Do you mean cranes and other machines that support weight? B: Sure, that’s a great example. A: But how do you analyze the structure of a machine? B: You can use the finite element method, for one. A: What’s that? B: It’s a numerical approach to analyzing complex structures like engines. 9 Suggested Answer Structural analysis is extremely important to mechanical engineering. Many large machines such as cranes and boat lifts are considered nonbuilding structures. Small machines also contain structural elements such as beams, plates, and columns. Structural analysis techniques like mechanics of materials and elasticity theory assess the strength and load-bearing capacities of machines and materials. The finite element method is capable of assessing much more complex systems. The finite element method uses computers to generate extremely accurate numerical approximations and probabilities. This makes it ideal for analyzing engines or entire vehicles. Failure analysis helps engineers assess what went wrong when a failure occurs. Understanding why failures occur helps engineers improve their designs to lower failure rates. 6 1D 1F 2T 34 Answer Key 3T 2B 7 1 failure analysis 2 corrosion 3 I was convinced 8 Suggested Answer A: I have the results of the failure analysis. B: What did you find? A: The results are still inconclusive. But we did find signs of corrosion. B: That makes sense. A: But it’s strange. There wasn’t enough corrosion present to cause a failure. B: That is strange. Did you do a complete metallurgical failure analysis? A: No, not yet. B: Let’s test for creep and fatigue. Maybe we can reproduce the failure that way. A: That’s a good idea. 9 Suggested Answer Date: January 16th Report Filed By: James Cordero, Lindsey Propst On January 14th, we concluded our failure analysis report. We found signs of corrosion present. Steps have been taken to ensure a complete metallurgical failure analysis will be undertaken. Although the likely cause of failure seems to be the corrosion, our results at this point are inconclusive. We recommend testing for creep and fatigue, perhaps we could test for failure by reproducing it in this way. 1 Suggested Answers 2 B brittle failure B Thermal shock B microscopic failure 5 Suggested Answer Unit 13 1 There are many different causes of material failure. Stress from heavy loads is a common cause of both brittle and ductile failure. Thermal shock can also cause failure in brittle materials like glass and cast iron. One of the most common causes of failure in metal parts is corrosion. Metal parts are also prone to buckling and creep. Fatigue is a cause of failure in many different materials. 2 Brittle and ductile failure are very different from one another. A brittle failure is also called a fracture. A brittle failure occurs suddenly, without any bending or other plastic deformation beforehand. A ductile failure is also called a yield. In a ductile failure, the material displays at least some plastic deformation before breaking. F yield G metallurgical failure analysis H buckle I failure theory J deform 4 metallurgical failure analysis 5 creep 6 But it’s strange Unit 14 1 Suggested Answers 1 There are many different types of destructive testing. Destructive testing refers to any type of test in which materials are tested to the point of failure. An extreme example of destructive testing is crash testing, which is Book 3 Answer Key typically performed on vehicles. Other destructive testing techniques include stress tests and hardness tests. Destructive tests are most useful for determining exactly how much force a material or system can withstand. This is extremely important if failure presents a safety concern. Destructive tests are not practical if the material or system is not produced in large quantities, or is expensive to produce. 2 There are several advantages of using non-destructive testing. Non-destructive tests analyze the properties of materials without causing any damage. This makes non-destructive testing ideal for situations in which the material or system is only produced in a very limited quantity, or in which the item to be tested is completely unique. One example of non-destructive testing is weld verification. Weld verification can be done in a variety of different ways without causing damage. Metallographic testing is another type of non-destructive test in which metals are examined under a microscope. 2 1D 3 2B Unit 15 1 Suggested Answers 1 There are many new frontiers of mechanical engineering research. MEMS, BioMEMS, and labs-ona-chip are complex machines that are small enough to fit in a handheld device. FSW techniques make it possible to weld materials that were once very difficult to weld, and may make rivets obsolete. Some fields, like nanotechnology, still exist primarily in theory. Mechanosynthesis is not yet possible with current technology. Biomechanics connects mechanical engineering to the medical field. Advanced prosthetics and artificial organs can improve the quality of life for patients around the world. 2 Lab-on-a-chip technology is incredibly significant to the medical world. Most laboratory tests require large and expensive machines, many of which are too specialized for ordinary doctors’ offices or even some hospitals. Lab-on-a-chip technology makes it possible to perform laboratory tests anywhere, often with instant results. This means that doctors can make diagnoses and begin appropriate treatments immediately. 3A A strain-stress curve B NFF C NDT 4 Appointment with: Brent Vale Client Info: Alan Turner with DCG Automotive (New Client) Mr. Turner is interested in testing a new material. He is interested in force deflection of a new material. He is also interested in stress-strain curves but did not specify what type of material. We should inform him of our crash testing policies and procedures during the initial meeting. It would also be beneficial to give him information about our materials testing machines. D force deflection E materials testing machine F extensometer Non-Destructive metallographic test weld verification G DT Destructive crash test stress test hardness test 5 Suggested Answer Sometimes test results are inconclusive and result in an NFF. The company offers a second round of testing. 6 1F 2T 2 1C 3T 7 1 stress test 2 non-destructive testing 3 When’s the next opening 4 You could meet with 5 destructive testing 6 crash tests 8 Suggested Answer A: How may I help you? B: I’m calling to ask about your testing services. Do you have materials testing machines? A: Yes, we do. What kind of materials testing do you need? B: I need to find out the force deflection of a new material. Is that something you can do? A: Yes, we can measure force deflection and stress-strain curves. Would you like to make an appointment? B: That sounds great. When’s the next opening? A: You could meet with an engineer on Thursday at 3. Does that work for you? B: That sounds great. Thank you. 9 Suggested Answer Date: Thursday the 16th – 3 pm 3 2D A lab-on-a-chip B prosthetics C MEMS D BioMEMS E rigidity F nanotechnology 4 1 Mechanosynthesis 2 artificial organ 3 biomechanics 4 composite G rivet H carbon fiber 5 FSW 5 Suggested Answer Carbon fiber is commonly used in composites because of its incredible strength and rigidity. 6 1F 2F 3T 7 1 area of expertise 2 BioMEMS 3 what kind of application 4 they’re chiefly used 5 lab-on-a-chip 6 very expensive 8 Suggested Answer A: I understand you work in the field of biomechanics. B: That’s correct. Much of my work involves prosthetics. Answer Key 35 Book 3 Answer Key A: I hear a lot about artificial organs. Can you tell me more about them? B: An artificial organ is a machine that takes the place of a human organ. A: And what is the significance of that kind of technology? B: Organ donors are hard to find. Sometimes people die waiting for organ transplants. A: Yes, I know. B: Imagine if everybody could get an artificial organ right away, without having to wait. A: It sounds like that could save lives. 9 Suggested Answer Wednesday, December 14th Charlie’s guest for this program is Dr. Ann Haley. Dr. Haley is a biomechanical engineer who works in the field of biomechanics. During the interview, Charlie asks Dr. Haley about artificial organs. Dr. Haley explains how a machine could take the place of a human organ. The interview also touches on how hard it is to find organ donors and how some people die waiting for a transplant. Tune in to learn how an artificial organ can save lives. 36 Answer Key Audioscripts Unit 1 Unt 3 Student: Instructor Matthews? I don’t think I quite understand what mechanical energy is. Instructor: Okay. Well, mechanical energy is the combined kinetic and potential energy in a mechanical system. Student: Hmm. I think I’m confused about the difference between kinetic energy and potential energy. Instructor: Think of it like this: Potential energy is energy that could be released in the future. But kinetic energy is in motion right now. Student: That’s what you said in class. But I don’t get how that works. Instructor: Well, picture a rubber band. When you stretch it, it has elastic potential energy. When you let go of it, that potential energy becomes kinetic energy. Student: Okay, I get it now. But what about thermal energy? Does that count towards mechanical energy? Instructor: Thermal energy is a kind of kinetic energy. So yes, it does. Student: Oh, that never occurred to me. So it’s kinetic because it’s actively performing work, right? Instructor: Exactly. And do you remember what causes the release of thermal energy? Student: It’s the movement of subatomic particles. Instructor: That’s absolutely right. Engineer 1: Zak, it looks like we’re still having problems with that prototype. Engineer 2: Are you talking about the gasoline engine? Engineer 1: No, the diesel engine. The connecting rod on cylinder two broke again. Engineer 2: That’s strange. I thought we just replaced it. Engineer 1: We did. That means the problem wasn’t just a faulty connecting rod. Engineer 2: Do you have any idea what the real problem is? Engineer 1: Well, unfortunately, it looks like the piston’s timing is off. Engineer 2: That could be a major problem. So the issue is somewhere in that combustion chamber? Engineer 1: Exactly. The piston is working too hard to move. That puts extra stress on the connecting rod. Engineer 2: Hmm. Do you think there’s something wrong with the fuel injection pump? Engineer 1: I didn’t think of that, but it’s certainly possible. Too much fuel would affect piston movement. Engineer 2: Can we replace the pump and see if that solves the problem? Engineer 1: We can give it a try. If that doesn’t help, I don’t know what will. Engineer 2: I’ll replace the fuel injection pump right away. Unit 2 Unit 4 Student 1: Hey, Stephanie. Do you know what will be on the quiz tomorrow? Student 2: I think it’s about the three ways to transmit heat. Should we go over each of them? Student 1: That’s a good idea. Let’s start with conduction. Student 2: If I remember correctly, conduction is when heat transfers through direct contact. Student 1: Yeah, I remember that. And specific heat is how well a material undergoes conduction. Student 2: Not exactly. I think you’re thinking of thermal conductivity. Student 1: Oh, you’re right. I always get those confused. Specific heat is the amount of energy you need to heat something. Student 2: Right. The second type of heat transfer is convection. Student 1: Like in an oven? Student 2: Exactly. Does convection only occur when a gas is present? Student 1: No, I’m pretty sure it can be any fluid. Because I know it happens in water, too. Student 2: Yeah, that sounds right to me. Okay, so the last type is radiation. Student 1: That’s easy. That’s heat transmitted through waves of particles. Student 2: Right, like heat from the sun. Student 1: All right. I guess that covers it. I think we’re ready for the quiz. Engineer: Hey, Alice, I need to go over the new project with you. Assistant: Sure, Steve. What’s the project? Engineer: We’re designing an engine for a motorcycle company. How much do you know about two-stroke engines? Assistant: Well, I learned about them in college. But I never actually worked on one. Engineer: Okay. So it sounds like you know the basics. Assistant: Right. I know there’s only one crankshaft revolution per power cycle. Engineer: And you know that more fuel enters the cylinder while the exhaust escapes? Assistant: Yes. I remember that. Engineer: Good. But it’s also important to remember that twostroke engines use two-stroke oil. Assistant: What’s the difference between that and other types of oil? Engineer: It’s for additional lubrication. In a two-stroke engine, the oil is actually mixed in with the fuel. Assistant: Hmm, that’s interesting. Is that because the crankcase is open on a two-stroke engine? Engineer: Yes, that’s right. Now remember, it’s really important to have the right fuel-to-oil ratio. Assistant: That makes sense. It sounds like if you don’t, the engine could burn out. Engineer: Exactly. Answer Key 37 Audioscripts Unit 5 Student 2: Do you want to go over some of the terms? Student 1: That’s a great idea. Can we review pitch first? Student 2: Sure. What is pitch? Student 1: Well, I think it’s the difference between a gear’s teeth. Student 2: Right. It’s the distance between a point on one tooth and the same point on the next tooth. Student 1: Oh yeah. And two gears in a gearset must have the same pitch, right? Student 2: Exactly. If they don’t have the same pitch, they don’t fit together properly. Student 1: That makes sense. So what’s the pitch circle? Student 2: The pitch circle is an imaginary circle that goes all around the gear. It follows the same contact points that determine pitch. Student 1: I remember now. And the pitch radius is the distance from the center of the gear to the pitch circle. Student 2: You got it. I guess you know more than you thought you did. Student 1: Yeah, I guess so. I think I’ll do fine on the exam. Engineer 1: Hi, David. Did you take a look at the malfunctioning engine? Engineer 2: Hi Janet. You’re right about it. It’s just not generating enough power. Engineer 1: I was thinking there might be a crack in the cylinder. Engineer 2: Yeah, that was my first thought. But I checked the cylinder and I couldn’t find anything. Engineer 1: Maybe the head gasket is loose. Did you check that? Engineer 2: Yeah. It was fine. Everything I checked was fine. Engineer 1: Hmm. What else did you look at already? Engineer 2: Let’s see. Oh, I checked the intake valve. Plenty of fuel is entering the chamber. Engineer 1: Well, all I can think of is that the fuel isn’t igniting every cycle. Engineer 2: That’s possible. What would cause that? Engineer 1: What about the spark plug? Engineer 2: Oh, of course. I never looked at that. Maybe it’s not firing correctly. Unit 8 Engineer 1: That’s what I’m thinking. Let’s check it out. Engineer 2: Good idea. Engineer: Hi, Tracy. Thanks for meeting with me. Manufacturer: Of course, Peter. What’s this problem you wanted Unit 6 to talk about? Engineer: Well, we ran into an issue with our new planetary Engineer: Okay, Mr. Swenson. I finished my assessment of your geartrain. manufacturing line Manufacturer: That’s not good. We’re supposed to begin Owner: Did you find any ways to speed up production? production next week. What’s the issue? Engineer: As a matter of fact, I did. Your serial robots have a Engineer: It looks like the spider is defective. The arms are limited range of motion. starting to bend. Owner: You think we can improve them? Manufacturer: That sounds pretty bad. Do you know what’s Engineer: Certainly. A greater radius would increase the reach of causing it? the machines’ manipulators. Engineer: We think there’s too much friction between the spider Owner: What effect will that have? and the sun gear shaft. Engineer: Each machine will cover more area. That way, you’ll Manufacturer: I see. So it’s not rotating correctly. Is that right? be able to use fewer machines on the production line. Engineer: Exactly. We need to adjust the design so it can rotate Owner: Hmm. And that means fewer components to maintain, smoothly with the planet gears. and fewer parts to replace. Manufacturer: That sounds simple enough. How long will it take Engineer: That’s exactly right. It will cut down your costs. to make the changes? Owner: That sounds promising. Do you have any other Engineer: I think we can correct the prototype in two or three suggestions? days. Engineer: I think you should increase the speed of rotational Manufacturer: Will that give you enough time to test the motion. geartrain? Engineer: It should. I really don’t want to delay production. Owner: You mean the machines’ RPM? Manufacturer: Well, I’d rather work out all the problems first. Engineer: Yes. Right now they’re pretty slow. Don’t start production until the prototype functions correctly. Owner: Are you sure that’s safe? Engineer: I understand. Engineer: Yes. They’re operating well below their maximum speed. And remember, you’re going to increase the rotational Unit 9 radius. That will change the angular velocity. Owner: Oh, right. So they’ll need to be faster anyway, just to Engineer: Dr. Franklin? Did you have a chance to review my cover the same area. recommendation? Owner: Yes, I got your email. You want a new drafting program? Unit 7 Engineer: Right. I think it will really improve our design process. Owner: Those CAD programs are expensive. Do we really need Student 1: I’m worried about the exam tomorrow. 38 Answer Key Audioscripts one? Engineer: I believe we do. For instance, it would help me out a lot on my current project. Owner: What are you working on? Engineer: I’m designing a new engine. And I need to make a model. Owner: Can’t you do that we the program we have now? Engineer: Not really. It’s much easier to manufacture models with the newer programs. The designs are already formatted for that purpose. Owner: I see. So what kinds of models can you create? Engineer: I could use a B-rep to create a manifold model. If that looks good, then I could create a non-manifold model. Owner: Hmm. Right now, we have to manufacture a prototype for that level of detail. Engineer: Exactly. And that requires time and materials. It gets expensive, especially when designs don’t work out. Owner: All right, you convinced me. It sounds like I should order this right away. Interviewer: How about robotic flow lines? Engineer: Yes, I designed four- and six-joint manipulators at my last job. Interviewer: That’s great. What is the most challenging aspect of robotics for you? Engineer: I’d say developing teach pendants is the most challenging aspect. But that’s what I like about it. Interviewer: What do you mean? Engineer: Programming a robot remotely can be frustrating. But at the same time, it’s very rewarding when it finally works correctly. Interviewer: I can understand that. Are you familiar with pneumatic machinery? Engineer: No, but I’m eager to learn more about it. I do have a lot of experience with hydraulics. Interviewer: I’m glad to hear that. Well, thank you for coming in today. Unit 12 Student: Professor Robbins, I don’t think I need to take this course. Instructor: Why is that, Heather? Engineer 1: Hey, Jerry. Can you spare a minute or two? Student: I’m a mechanical engineering student. Why do I need to Engineer 2: Sure, Melissa. Do you want to talk about the drill study structural analysis? press project? Instructor: Well, structural analysis applies to machines as well. Engineer 1: Yeah, that’s it. I think we can improve its product Plenty of machines are considered nonbuilding structures. lifecycle. Student: Like what? Engineer 2: What in particular do you want to improve? Instructor: You know about mechanical engineering, so you tell Engineer 1: The team and I were looking at the lifecycle me. What kinds of machines have to support heavy loads? assessment. We think we need to reduce waste. Student: Do you mean construction equipment? Engineer 2: Reducing our environmental impact is definitely Instructor: Sure, that’s a great example. Cranes, excavators, good. What area do you think we need to work on? and even small forklifts carry structural loads. Engineer 1: Well, the team agrees that we should cut back on Student: I guess I never thought of that before. But how do you packaging. If we simplify it, we’ll reduce cost and waste. analyze the structure of a machine? Engineer 2: That makes sense. Instructor: There are a number of ways. Think about mechanics Engineer 1: But personally, I think we need to pay the most of materials. What do you think you could use that for? attention to material intensiveness. Student: Well, I guess it could help determine how much weight Engineer 2: You’re right. If we rethink our material selection, we a machine can lift. could reduce toxicity. Instructor: Exactly. The finite element method is helpful as well. Engineer 1: That’s what I’m hoping. But I’m afraid it’ll be hard to Student: What’s that? convince the rest of the team. Instructor: It’s a mathematical approach to assessing complex Engineer 2: The trouble is getting everyone to agree. structures. Mechanical engineers use it for analyzing Engineer 1: You’re right. We really need better systems systems like engines. engineering on this project. Student: Hmm. I guess that all makes sense. Unit 10 Unit 11 Unit 13 Interviewer: You must be Emily. I’m Robert. How are you doing today? Engineer: I’m a little nervous, actually. This is my first job interview in a while. Interviewer: That’s perfectly understandable. Can you tell me about your engineering experience? Engineer: Well, for the past ten years, I was a robotics engineer. Interviewer: And what kind of automation did you work with? Engineer: Most of my experience is with serial robots. Engineer 1: Hey Lindsey, I have the results of the failure analysis. Engineer 2: That’s great, James. What did you find? Engineer 1: Well, the results are still inconclusive. But there are definitely no signs of corrosion. Engineer 2: Really? I was convinced there would be corrosion. Engineer 1: I know, I thought so, too. That’s why we did a more complete metallurgical failure analysis. Engineer 2: And what kind of results did you get? Engineer 1: Well, there are signs of creep in several connected Answer Key 39 Audioscripts parts. Engineer 2: That makes sense. Engineer 1: But it’s strange. The degree of deformation wasn’t enough to cause a failure. Engineer 2: You’re right. Do you think there’s any chance that thermal shock was a factor? Engineer 1: You know, I didn’t consider that. But I suppose it’s possible. Engineer 2: Let’s test for thermal shock. Maybe we can reproduce the failure that way. Engineer 1: That’s a good idea. Engineer 2: If that caused the fracture, we need better temperature control. Engineer 1: Yeah. I’ll get that test started as soon as possible. Unit 14 Employee: Corelli Engineering. How may I help you? Client: Hi there. I’m calling to arrange some testing for an engine. Employee: Of course, sir. Have you used our materials testing services before? Client: No, I haven’t. Employee: Okay. And what kind of testing are you interested in? Client: Well, I’m hoping to have the individual parts analyzed and tested first. Then I want to run a stress test on the whole engine. Employee: All right. We do offer comprehensive non-destructive testing. Would you like to make an appointment with an engineer? Client: That would be great. When’s the next opening? Employee: Let’s see. You could meet with Brent Vale on Tuesday at two o’clock. Does that work for you? Client: Yes, that sounds good. Employee: And what is your name, sir? Client: My name is Alan Turner. I’m with DCG Automotive. Employee: Okay. And you want to discuss both non-destructive and destructive testing, is that correct? Client: That’s right. Oh, one more thing. Do you do automotive crash tests? Employee: Yes, we do. I’ll tell Mr. Vale that you’re interested in that, too. Client: Great. Thank you. Unit 15 Reporter: I’m here with Dr. Ann Haley, a mechanical engineer. Dr. Haley, thank you for being on the program. Engineer: Thank you for having me, Charlie. Reporter: Dr. Haley, I understand you have a very specific area of expertise. Engineer: That’s correct. I work primarily with BioMEMS. Reporter: And what kind of application do these BioMEMS devices have? Engineer: Right now, they’re chiefly used in the medical field. Reporter: I see. Now, Dr. Haley, I hear a lot about this lab-on-achip technology. Can you tell me a little about that? Engineer: Well, a lab-on-a-chip is related to BioMEMS 40 Answer Key technology. It’s basically a computer chip that can perform laboratory tests. Reporter: What is the significance of that kind of technology? Engineer: Well, as you probably know, medical tests can be very expensive. They also take a lot of time. Reporter: Right. Last time I was sick, it took weeks to get results back. Then I had to wait another week just to get an appointment. It was terrible. Engineer: Exactly. Now imagine getting results instantly, right there in your doctor’s office. Reporter: That sounds great to me.
