Practice Test: Technology/Engineering (70)

Answer Key, Sample Responses, Evaluation Chart, and Score Calculation Tool

Answer Key

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Question Number	Your Response	Correct Response (show answershide answers)	Related Objectives and Rationale (show objectives & rationaleshide objectives & rationales)
1	Answer to question 1	C	Objective 001 The length for the living room and bedroom is 20 feet plus 16 feet or 36 feet . Multiplying 36 feet in length by 15 feet in width gives an area of 540 feet (Incorrect Response A). However, 540 feet must be multiplied by 3 since a board is 4 inches wide (3 boards needed per foot). Since 10% waste has to be taken into account, this excludes 1,620 feet (Incorrect Response B). The 10% waste is an additional 162 feet of board (10% of 1,620 feet ), bringing the total to 1,782'. Rounding, the estimate would be 1,800 feet (Correct Response C). Incorrect Response D exceeds what would be needed for just the living room and the bedroom.
2	Answer to question 2	C	Objective 001 Bad wheel bearings cause wheels and tires to wobble and/or vibrate, increasing friction while decreasing acceleration and distance traveled. By using better wheel bearings, the acceleration (initial speed) will increase, and the car will travel a further distance since friction is decreased. Since acceleration increases, the initial speed of the car will increase (Correct Response C). Since the distance will increase, the slope will not decrease (Incorrect Response A). Since the distance traveled will increase with the speed, the car will travel faster with each second and therefore the entire slope will adjust, not just the first 1.5 seconds (Incorrect Response B). The distance traveled will increase, not decrease (Incorrect Response D).
3	Answer to question 3	B	Objective 001 Aerobic wastewater treatments use oxygen-feeding bacteria and certain microbes to break down wastewater contaminants and clean the water (Correct Response B). While compressed air (Incorrect Response A) is used to remove solids and break up compacted materials, it is gravity and pumping systems that move liquid waste. Carbon (Incorrect Response C) is used to remove contaminants and decrease particle size. As temperature increases, the pressure of a liquid increases causing the liquid to become more volatile. A more volatile liquid or gas will become problematic and, therefore, will not increase efficiency (Incorrect Response D).
4	Answer to question 4	B	Objective 001 The sum of two numbers expressed in scientific notation, where both expressions are in terms of the same power of 10 (exponent), can be found by adding the first parts (coefficients) and keeping the exponent the same. This can be shown arithmetically as follows: the quantity 3.5 times 10 to the third power plus the quantity 3.5 times 10 to the third power equals the quantity 3.5 plus 3.5 times ( 10 to the third power ) = (7) times (1,000) = 7,000 (Correct Response B). Incorrect Response A is the average of two numbers. Incorrect Response C is found by leaving the coefficients of the numbers unchanged and adding the exponents. Incorrect Response D comes from adding the coefficients of the numbers and adding the exponents.
5	Answer to question 5	B	Objective 001 The mass is found by multiplying the density of copper by the volume of the solid. In this case, the solid is a right rectangular prism, and its volume is V = l times w times h, where V, l, w, and h represent volume, length, width, and height, respectively. Therefore, the volume of the solid is 4.5 centimeters times 4.5 centimeters times 50 centimeters = 1,012.5 centimeters cubed , and the mass is 1,012.5 centimeters cubed times 8.96 grams per centimeters cubed = 9,072 g. The problem asks for the mass to be expressed in kilograms, so this answer must be converted as 9,072 grams times 0.001 kilograms per grams = 9.072 kg. Finally, since the measurements are given to two significant figures, the answer must be rounded to 9.1 kg (Correct Response B). Responses C and D are incorrectly reached due to an error when converting from grams to kilograms. Responses A and D are incorrectly reached due to not multiplying the volume by the mass.
6	Answer to question 6	B	Objective 001 The area of a circle can be calculated using the equation a = pie r squared , where a represents the area, r represents the radius, and pie is a specific irrational number. In this problem, the original area equals 144 pie square feet, and the final area equals 576 pie square feet. The factor requested can be found by dividing the final area by the original area, yielding 576 pie divided by 144 pie = 4 (Correct Response B). In general, if a quantity is directly proportional to the square of a particular variable, and the value of the variable is multiplied by a factor of x, the resulting quantity will increase by a factor of x squared . Incorrect Response A is reached by assuming that a doubling of the radius would result in a doubling of the area. Incorrect Response C is reached by assuming that the scale factor (4) should be cubed. This would have been correct for the volume of a spherical object. Incorrect Response D is reached by assuming that an increase of 12 in the radius will increase the area by the same amount.
7	Answer to question 7	D	Objective 001 The greatest clearance will occur for the smallest allowable dowel diameter (8.5 mm minus 0.1 mm = 8.4 mm) and the largest allowable hole diameter (9.0 mm + 0.1 mm = 9.1 mm). This maximum clearance will be the difference between the diameters (9.1 mm minus 8.4 mm = 0.7 mm) (Correct Response D). Incorrect Response A assumes that the greatest clearance would be equal to the greatest tolerance. Incorrect Response B assumes that the greatest clearance would be equal to the sum of the tolerances. Incorrect Response C assumes that the tolerances have no effect on the greatest clearance. It is incorrectly calculated that the greatest clearance is equal to the difference (9.0 mm minus 8.5 mm = 0.5 mm).
8	Answer to question 8	C	Objective 001 The volume of a sphere can be calculated using the formula V = 4 thirds pie r cubed , where V represents the volume, pie is an irrational number, and r represents the radius. This formula shows that the volume is directly proportional to the cube of the radius. In general, if a quantity is directly proportional to the cube of a particular variable and if the value represented by the variable is multiplied by x, the resulting quantity will increase by a factor of x cubed . Since 25.2 divided by 8.4 = 3, the value represented by the variable r is increased by a factor of 3. Hence, if the smaller sphere has a volume of V, then the larger sphere must have a volume of 3 cubed V or 27.0V (Correct Response C). Incorrect Response A assumes that doubling of the radius leads to an increase in volume by a factor of 8, not understanding that this was just a special case of the x cubed rule. Incorrect Response B results from assuming that the volume scale factor should be x cubed over 2 . Incorrect Response D comes from assuming that the volume scale factor should be 2 x cubed .
9	Answer to question 9	D	Objective 002 Since 1 inch in the plan represents 20 actual feet, 11.25 multiplied by 20 will yield 225 feet (Correct Response D). Incorrect Responses A, B, and C all round the 11.25 inches to 11 inches before doing any calculations, and the question states to round to the nearest foot. Incorrect Response A is the result of not multiplying the inches by the feet. Incorrect Response B is the result of multiplying 11 inches by 2 feet, not 20 feet. Incorrect Response C is the result of multiplying 20 feet by 11 inches, not 11.25 inches.
10	Answer to question 10	D	Objective 002 An assortment of building materials are provided in the question. The masking tape (Correct Response D) is the only adhesive material used to attach these construction materials, and since it is limited to a very small amount, it constrains the project more than the amount of the materials in Incorrect Responses A, B, and C.
11	Answer to question 11	C	Objective 002 Testing is a standard practice for quality control. If several of the finished products show defects, the entire production run might be discarded (acceptance sampling). Testing at numerous stages of production helps identify where a production problem is occurring to prevent the problem in the future (Correct Response C). Any disruptions to production, Incorrect Responses A and B, are not economically prudent: Errors are fixed during the production process, and production is not stopped. It is a standard quality-control process to inspect parts and materials prior to production, eliminating the possibility that defective parts would be used in the production process; the possibility of material error would have already been exhausted (Incorrect Response D).
12	Answer to question 12	A	Objective 002 Computer-aided engineering ( C A E ) software tools are used to simulate the effect on a part or product of various environmental and/or physical conditions such as weather, loads, or forces (Correct Response A). While these tools use mathematical calculations to evaluate the part or product, it is not the primary reason for the simulation (Incorrect Response B). Criteria and constraints for a product are determined prior to the development of the product; while problems with specific criteria or constraints may be discovered with testing, Incorrect Responses C and D are not the most important reason for the simulation.
13	Answer to question 13	C	Objective 002 The first step in the problem-solving process is to define the problem. In this case, the specific problem has not been determined. Therefore, the team will need to investigate each possibility systematically before solving the problem (Correct Response C). Since the cause of the problem is not determined, it is unnecessary to purchase replacement parts that may not be needed (Incorrect Response A). Incorrect Response B would recreate the same issue as the initial problem, just with a smaller pool and filter. Incorrect Response D is irrelevant as it does not keep debris from the water.
14	Answer to question 14	A	Objective 002 Reverse engineering is a method of determining the design features of an existing product by taking the product apart to see how it was made (Correct Response A). Incorrect Responses B, C, and D are not specifically about the reverse engineering process; however, reverse engineering might be a reasonable first step toward improving upon (Incorrect Responses B and D) or finding a new use for (Incorrect Response C) an existing product.
15	Answer to question 15	B	Objective 002 The dimension labeled X can be determined indirectly as 51 feet minus the quantity 21 feet plus 25 feet equals 5 feet . Since each actual foot in the house is represented by 0.5 inch in the floor plan, the dimension labeled X, which is equal to 5 feet in the house, is represented by 5 times 0.5 = 2.5 inches in the floor plan (Correct Response B). Incorrect Response A comes from misreading the floor plan, assuming that X represents only the distance from the dotted line to the bathroom wall on the right, and estimating it to be 2.0 inches. Incorrect Response C is a rough visual estimate. Incorrect Response D comes from calculating 51 minus the quantity 21 plus 25 equals 5 and neglecting to use the scale factor to convert the 5 feet of real floor to 2.5 inches of the floor plan.
16	Answer to question 16	B	Objective 002 The students have already designed and tested their solution with 80% of the trash being collected. The only step left is to address the issue of the remaining 20% of uncollected trash (Correct Response B). In Incorrect Response A, the testing has already been done. In Incorrect Responses C and D, budgetary constraints and aesthetics are not relevant since the solution is complete.
17	Answer to question 17	C	Objective 003 Animals will move from their habitats or resting place when they sense a disruption in the water by any vehicle, including an RC boat. In addition, habitats or plants near debris being removed would be disrupted and could get tangled in the net (Correct Response C). An electric boat is no more invasive to park-goers than any other boat (Incorrect Response A); because the boat is electric, it would be quiet. Picking up trash does not affect how much someone litters (Incorrect Response B). While waves from a boat can cause erosion (Incorrect Response D), there is no evidence that this RC boat would be driven at high speeds to create larger waves.
18	Answer to question 18	B	Objective 003 The key statement in the question is the patient’s compliance in wearing the device, which indicates the importance of aesthetics. Appearance is the issue a patient will find concerning (Correct Response B). Incorrect Responses A, C, and D are related to the function of the device, allowing the data to be collected and transmitted to the doctor. While function is important, it is not something the patient will be aware of on a daily basis.
19	Answer to question 19	A	Objective 003 The first step of the design process is always to state the problem (Correct Response A). Incorrect Responses B, C, and D will be considered in future steps of the design process, as the engineers collect information and brainstorm solutions to the problem.
20	Answer to question 20	D	Objective 003 The main advantage of nuclear energy is it is a low-carbon energy source and has one of the smallest carbon footprints (Correct Response D). Response A is incorrect because there is an impact to the environment as the mining and enrichment of uranium cause erosion. Response B is incorrect because it is expensive to build a nuclear power plant. Response C is incorrect because nuclear energy is not a long-term solution to energy needs as it requires uranium and thorium to create energy; these resources will be depleted just like fossil fuels.
21	Answer to question 21	B	Objective 003 The key phrase in the question is that the homeowners wish to decrease emissions and dependence on nonrenewable energy. Heat pumps are more eco-friendly than gas baseboards as they run on electricity, not gas. However, the amount of nonrenewable energy used depends on the utility company generating the electricity, their generating capacity, and the fuel sources they use (Correct Response B). Newer heat pumps have a backup heat source to access if the temperature outside gets too low (Incorrect Response A). Incorrect Responses C and D are not relevant as they do not pertain to emissions or energy sources: While heat pumps can be prone to mold (Incorrect Response C), they can also be ductless systems, but this does not affect emissions, and maintenance costs of baseboard units (Incorrect Response D) are higher, but, again, this does not affect emissions.
22	Answer to question 22	A	Objective 003 In the problem-solving process, when selecting members of a focus group, members should consist of those who are most familiar with the problem and who are invested in the solution: in this case, the people who regularly experience the driving commute into and out of the city (Correct Response A). The individuals described in Incorrect Responses B, C, and D do not necessarily experience this commute by car.
23	Answer to question 23	C	Objective 003 Human factors engineers focus on ergonomics (human factors principles) when designing systems. There are five human factors: physical, cognitive, social, emotional, and cultural. Therefore, the engineers will focus on consumers’ impression or understanding regarding security (Correct Response C). Human factors engineers do not focus on material properties (Incorrect Responses A and B) and are not concerned with suppliers (Incorrect Response D).
24	Answer to question 24	B	Objective 003 Demographic data include socioeconomic information such as age, gender, ethnicity, and income. Therefore, the information collected will allow marketing designs to be tailored toward this particular demographic group (Correct Response B). The data collected do not pertain to the technical aspects of the ad designs (Incorrect Response A), volume of sales (Incorrect Response C), nor the techniques used in the marketing process (Incorrect Response D).
25	Answer to question 25	A	Objective 003 Prototyping allows the engineer to attempt different iterations of the same product: testing the prototypes against the criteria and constraints set forth in the engineering design process. In order to perform effective testing, a measurable set of criteria must be established (Correct Response A). Racing the prototypes (Incorrect Response B) tests only one criterion: speed. Collecting opinions on desirable bicycle traits (Incorrect Response C) does not test the effectiveness of the various drivetrains. The method of discussing strengths and weaknesses of each drivetrain and coming to a consensus (Incorrect Response D) is not measurable.
26	Answer to question 26	D	Objective 004 Masking tape placed on slippery surfaces will create enough surface traction to stop a drill bit from slipping (Correct Response D). A center punch (Incorrect Response A) can chip acrylic. Cracking can occur in acrylic at the wrong drill speed (Incorrect Response B). Acrylic is a slippery material regardless of paint (Incorrect Response C).
27	Answer to question 27	B	Objective 004 Because acrylic cracks easily, using a consistent slow speed when drilling (Correct Response B) will prevent the acrylic from shattering. In addition to causing acrylic to shatter, running a drill at a high speed (Incorrect Responses A, C, and D) can also cause the acrylic to melt.
28	Answer to question 28	A	Objective 004 Maintaining balance with stable footing (Correct Response A) is a primary safety precaution when operating all power tools. While Incorrect Responses B and D are common safety practices, they are not the most important. OSHA requires hearing protection (Incorrect Response B) when exposed to sound at 85 decibels or higher for eight hours: Since power tools range from 80 to 120 dBA, hearing protection is suggested, and typical power tool use occurs for less than eight hours at a time. When cutting, power tools should be moved away from the body, but not all power tools cut (Incorrect Response D) (sanders for example may use circular or back-and-forth linear motion). Response C is incorrect because a trigger should remain locked until the tool is in use.
29	Answer to question 29	C	Objective 004 A POP rivet is used when access to the back side of the work piece is limited (Correct Response C). Incorrect Responses A, B, and D are not practical applications for a blind rivet. Response A is incorrect because POP rivets are not watertight. Response B is incorrect because the number and pattern of POP rivets required depends on application, material, and the nature of the final product.. Response D is incorrect because disassembling rivets requires a proper tool: It is not a standard practice to use rivets when later disassembly may be required.
30	Answer to question 30	A	Objective 004 The main reason Computer Numeric Control (CNC) is used is that it provides precise numeric control of a machine tool (Correct Response A): It can be up to 10 times more accurate than hand cutting, as well as faster. Incorrect Responses B, C, and D are not the main advantage over handheld routers. CNC machines can cut a wider range of materials, and there is little tool setup and operator skill needed. It does take time, however, to program the machine, which is most associated with its precision cutting.
31	Answer to question 31	C	Objective 004 The first, and most important, step when administering first aid to a person with a puncture wound is to stop the bleeding by applying direct pressure to the wound (Correct Response C). If the bleeding is extremely severe or if it does not stop after 10 minutes of firm direct pressure, then call 9-1-1 (Incorrect Response A). Once the bleeding has stopped, wash the wound with warm water (Incorrect Response D) and gentle soap. After the wound is cleaned, apply an antibiotic ointment and a sterile bandage (Incorrect Response B).
32	Answer to question 32	C	Objective 004 While many home-remedy solutions such as baking soda (Incorrect Response A), vinegar (which contains acetic acid) (Incorrect Response B), and hydrogen peroxide (Incorrect Response D) may be good cleaners and disinfectants, none of them are recommended for cleaning up blood spills on workplace floors. The only recommended chemicals for this application are a 1 to 10 solution of chlorine bleach (Correct Response C) and water or a commercial cleaner specifically designed for workplace bodily fluid cleanup.
33	Answer to question 33	A	Objective 004 All four choices are examples of calipers. Correct Response A is an example of a type of spring joint caliper known as a divider or a compass. Its two straight legs make it most useful for measuring distances on a flat surface. This caliper is not a direct measurement tool since it has no graduations. It is an example of a transfer measurement tool because it is used to transfer a measurement from one object to another. An actual measurement can be made if the second object is a ruler. This tool is also used for scribing arcs and circles. Incorrect Responses B and C are outside and inside spring joint calipers, respectively. They are also transfer measurement tools for measuring the outside and inside dimensions of physical objects. Today, they have been mostly replaced by digital calipers. Incorrect Response D is an example of a hermaphrodite caliper. This type of caliper has one leg with a curved end and one with a straight end. The curved end is used to hook around the edge of an object while the straight end is used for scribing or measuring a distance from the edge.
34	Answer to question 34	B	Objective 004 For a second tangent line to be parallel to a first tangent line, it must be tangent to that circle at a point that is 180 degrees around the circle from the first tangent line. Any line that joins two points 180 degrees apart around a circle must be a diameter of that circle since it divides it perfectly in half. Therefore, Response B is correct. Incorrect Responses A, C, and D all employ constructions that make use of the endpoints of the originally drawn tangent line. Since these endpoints are not defined in the problem, none of the resulting constructions are completely defined. Hence, each construction could result in an infinite number of different drawings, most of which would not lead to the determination of the diameter of the circle.
35	Answer to question 35	C	Objective 004 When welding some metals such as aluminum and magnesium, it is very important to protect the high-temperature metal from the oxygen and water vapor that are in the air. For this reason, an inert shielding gas is used (typically a combination of helium and argon). The most common welding process for these metals is gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding (Correct Response C). Shielded metal arc welding (Incorrect Response A) is mostly used for welding steel and iron: It is not commonly used with nonferrous metals such as aluminum and magnesium because the shielding gas, which is given off by the flux, does not tend to be extensive enough to protect these metals from oxidizing. As the name implies, oxyacetylene welding (Incorrect Response B) uses a combination of pure oxygen and acetylene gases. The presence of pure oxygen precludes the use of this welding technique with aluminum and magnesium because these metals will react with the oxygen, creating oxides that interfere with the welding process. Since carbon arc welding (Incorrect Response D) is carried out without any mechanism to shield the metal from the oxygen and water vapor in the air, it is not appropriate for welding aluminum and magnesium.
36	Answer to question 36	D	Objective 005 Roll forming is a common method for making wall paneling. Galvanized steel can be produced from either cold-rolled or hot-rolled steel (Correct Response D). Galvanizing is covering the steel with molten zinc that then can be powder coated. Forging (Incorrect Response A) is used to shape a metal through compression; it should not be used on galvanized steel due to the toxicity of the zinc. Extruding (Incorrect Response B) is a process used to form material by forcing it through a die; it is commonly used for complex parts. Die casting (Incorrect Response C) is forcing metal into a mold; it is often used for intricate shapes.
37	Answer to question 37	A	Objective 007 Galvanizing is used in construction to prevent rusting; it will last for years in harsh environments (Correct Response A). Galvanized steel is not used for its insulative properties (Incorrect Response B). Powder coating the galvanized steel (Incorrect Response C) can enhance the appearance; however, it is not a functional requirement. Galvanized sheet steel is flexible (Incorrect Response D), but this steel has been corrugated, which makes it less flexible.
38	Answer to question 38	C	Objective 005 One of the fastest methods to manufacture plastic prototypes is 3-D printing (Correct Response C); it is an additive manufacturing process, adding layer upon layer of plastic, and there are no tooling costs and little lead time. CAD can be used to design the product and CAM to manufacture the prototype (Incorrect Response A), but this would require more lead time and a higher manufacturing cost. Injection molding (Incorrect Response B) has a higher lead time and there is a tooling cost. Manual machining (Incorrect Response D) is not as precise as using CAD software and a 3-D printer.
39	Answer to question 39	C	Objective 005 Forging (Correct Response C), the process of compressing heated steel under extreme pressure, is used to harden and strengthen steel. Molding (Incorrect Response A) is used to form a material in some sort of frame. Casting (Incorrect Response B) is the process of melting a material and pouring it into a mold to shape it. Rolling (Incorrect Response D) is a deformation process where steel is passed between rollers, making it thinner.
40	Answer to question 40	B	Objective 005 The more axes a milling machine possesses, the more complex its potential products (Correct Response B). A three-axis machine moves a spindle on the x, y, and z directions while the workpiece is fixed in one position; it is used for simple parts. In contrast, machines with four and five axes rotate the fixture, speeding up the machining process and increasing accuracy. While Incorrect Responses A, C, and D are also plausible, the most important advantage of more axes is processing different sides of the workpiece without changing the position, improving processing efficiency.
41	Answer to question 41	A	Objective 005 By custom producing vehicles, start-up companies can alter a vehicle to improve performance, meeting consumer demand (Correct Response A). Response B is incorrect because labor costs would be incurred in both types of production. Response C is incorrect because mass production is used to produce identical products, not custom. Response D is incorrect because it takes a large investment to start mass producing a vehicle, which is risky for a new product; custom producing the product initially would keep costs down until the vehicle proves successful and demand increases.
42	Answer to question 42	D	Objective 005 Polymerization is a process that takes small molecules called monomers and combines them together into very long molecular chains called polymers. The original substance tends to be in the form of a viscous fluid. After polymerization, the longer polymer chain molecules form a microscopic mesh, giving the newly formed plastics a semi-rigid structure (Correct Response D). Ball bearings (Incorrect Response A) are produced by a process called cold heading where short pieces of metal wire are smashed between hemispherical forms. While some textiles (Incorrect Response B) are made from plastic fibers (which are made through polymerization), the actual textiles are woven on looms from a variety of different types of fiber. Metallic wire (Incorrect Response C) is made by drawing a thick metal rod through dies that stretch and narrow the rod until it is at the specified gauge.
43	Answer to question 43	A	Objective 005 Cracking is a process used to break up the complex long-chain hydrocarbon molecules found in crude oil and produce simpler short-chain hydrocarbon molecules (Correct Response A), thereby yielding lighter oils such as diesel fuel and gasoline. Impurities (Incorrect Response B), such as sulfur and nitrogen, are removed using a process called hydrotreating. Crude oil must first undergo a distillation process where it is separated into different products such as tar and naphtha, a mixture used to make plastics (Incorrect Response C). A quality assay (Incorrect Response D) is an evaluation of the chemical makeup of a particular crude oil in order to determine its compatibility with a particular refinery and to check for possible environmental or other problems.
44	Answer to question 44	D	Objective 005 Due to highly detailed die molds and high-pressure molten metal injection, die casting (Correct Response D) produces the most finely detailed metal parts requiring the least amount of finishing. As the name implies, sand casting (Incorrect Response A) is a casting process where the mold is made out of sand held together with a binder. While this process is less expensive than others, the mold is limited in terms of detail, finish, and ability to withstand high-pressure injection. In conventional mold casting (Incorrect Response B), the molten metal is poured into the mold under the influence of gravity. Because the molten metal is not injected under high pressure, the results are not as finely detailed as those from die casting. Centrifugal casting (Incorrect Response C) is primarily used to manufacture stock materials in axially symmetric shapes, such as pipes and flanges. These materials typically require machining before they are ready to be used. Centrifugal casting is not generally used to create specific finished parts.
45	Answer to question 45	B	Objective 005 The change described in the question will result in a 33% increase 1 seventy fifth divided by 1 one hundredth in time and money spent on testing. This increase will have to be added directly to the overall production costs (Correct Response B). On the other hand, this change could have a positive influence on long-term profits (Incorrect Response A), sales (Incorrect Response C), and marketing (Incorrect Response D) since it should result in a higher-quality product.
46	Answer to question 46	C	Objective 005 Robots are best suited for precise, repetitive tasks that do not require subtle thinking or dealing with unpredictable situations. Spot-welding body parts (Correct Response C) is a common, suitable robotics manufacturing application. Troubleshooting part failures (Incorrect Response A) requires complex and adaptable reasoning, often dealing with unforeseen circumstances. Adding custom details (Incorrect Response B) is a case-by-case procedure that is custom in nature and, therefore, not well suited for robotics. Final product inspection (Incorrect Response D) needs to be performed by a human who can spot unforeseen problems.
47	Answer to question 47	D	Objective 006 An antenna is effective only over a small range of wavelengths. An antenna receiving a directly transmitted audio signal would need to cover wavelengths from about 15 kilometers to 15,000 kilometers. Therefore, the carrier signal (a modulated waveform used to convey information) is instrumental in getting the source signal from its origin to its intended location, the antenna (Correct Response D). Responses A, B, and C are also correct depending on the type of modulation; however, their relevance is not important if the signal does not reach its destination, making them incorrect choices.
48	Answer to question 48	C	Objective 006 Acoustical engineers are concerned with sound quality. By studying how whales and dolphins communicate sounds with broad frequency bandwidth through various underwater interference (Correct Response C), underwater transmission could be enhanced and delays in communication averted. Incorrect Responses A, B, and D are not areas studied by engineers working with acoustics in regard to underwater communication.
49	Answer to question 49	B	Objective 006 A local area network (LAN) will allow networked peripherals, such as printers and scanners, to be shared by all workers on the network (Correct Response B). A single-use software license (Incorrect Response A) does not allow multiple installations even if all computers are on the same network. A LAN should not have any effect on the performance of computers or peripherals (Incorrect Response C). A LAN would not reduce the likeliness of technical difficulties (Incorrect Response D); on the contrary, there is a possibility of increased technical difficulties due to the increased complexity of the connections.
50	Answer to question 50	D	Objective 006 Computers typically send and receive data in the form of a digital signal (Correct Response D). In some cases, a modem may convert a computer's outgoing digital signal to an analog one, but the signal will have to be converted back to a digital signal before it can be received by another computer. The output from a microphone (Incorrect Response A) is analog, not digital. The input to an amplifier (Incorrect Response B) from many devices is an analog signal. The output from any speaker (Incorrect Response C) is a sound wave, which is analog by definition.
51	Answer to question 51	B	Objective 006 Since a digital file is merely a series of binary digits, it can be copied many times with very little deviation from the original file (Correct Response B). In contrast, when copying an analog file, there is always some loss of information as well as the addition of some extraneous noise. A natural sound wave is a smooth analog curve, and a digital signal can approximate this curve with a very fine step function, but it will never be indistinguishable from a true natural sound wave (Incorrect Response A). An analog signal is qualitatively more similar to a natural sound wave, but its fidelity to the original is limited by the sensitivity of the recording device and by the level of shielding from outside noise sources. Both analog and digital signals can be transferred electronically (Incorrect Response C). A CD is a digital storage device; therefore, an analog signal cannot be directly stored on a CD (Incorrect Response D).
52	Answer to question 52	D	Objective 006 Electromagnetic waves can propagate through the vacuum of space, but sound waves rely on a carrying medium, such as air, for propagation. This is because sound is transmitted via collisions between the molecules in the carrying medium (Correct Response D), whereas electromagnetic waves are oscillating electric and magnetic fields. The relative rates of attenuation over distance of sound waves and electromagnetic waves depend on many factors, but this does not explain why sound waves cannot travel through empty space (Incorrect Response A). Gravity (Incorrect Response B) does not play a role in the propagation of sound waves. The amplitude of electromagnetic waves is measured in electromagnetic field strength, and the amplitude of sound waves is measured in ambient pressure; therefore, they cannot be compared (Incorrect Response C).
53	Answer to question 53	A	Objective 006 In fiber-optic telephone systems, a digital signal is transmitted by a laser through an optical cable. Because it is a digital signal, it is composed of binary digits represented by the light source turning on and off extremely rapidly (Correct Response A). Optical cables contain glass fibers that are not used for conducting electrical current (Incorrect Response B). Being digital in nature, the information is contained in the on and off switching of the light source and not in changes in wavelength (Incorrect Response C) or color (Incorrect Response D).
54	Answer to question 54	B	Objective 007 Expansion joints allow a structure to expand and contract, maintaining its structural integrity after deformation; therefore, the material for these joints would need to be elastic to accommodate this expansion/contraction (Correct Response B). The type of expansion joint chosen would vary with the application. Incorrect Responses A, C, and D would be relevant depending on the materials used in the type of joint chosen, while elasticity is common to all joints.
55	Answer to question 55	A	Objective 007 Prototyping in science and engineering is a way to produce knowledge. A good practice to produce knowledge is to design a product, test and review it, scrap the design, and redesign it with the knowledge previously gained (Correct Response A). Incorrect Responses B and C do not produce knowledge: Incorrect Response B records knowledge, and Incorrect Response C is a form of evaluation or validation. Incorrect Response D is unnecessary as the source of the water is irrelevant to the test.
56	Answer to question 56	B	Objective 007 Since there is a time constraint, the quickest option is to replace the soil; clay soil can be removed with proper excavation equipment quickly (Correct Response B). Redesign (Incorrect Responses A and C) is time and labor intensive, requiring architects and engineers. Removing clay soil is a more desirable alternative than compaction (Incorrect Response D): To compact clay, you have to load it with water and then force it from the “voids.” This can be accomplished with a rammer, roller, or sheepsfoot, all of which would take longer than digging out the clay.
57	Answer to question 57	D	Objective 007 A bimetallic-strip thermostat contains a flat strip of metal formed in the shape of a coil. As the ambient temperature changes, the coil winds tighter or looser according to the direction of the temperature change. The metal strip consists of two different metals bonded together: one metal is on the inside of the bend of the strip, and the other is on the outside. Since the two metals have different coefficients of thermal expansion, they expand and contract at different rates as the temperature changes (Correct Response D). This causes the strip to bend one way or the other, actuating the heating or cooling switches. Incorrect Response A might make sense for very fast and extreme changes in temperature since the metal with the greater specific heat would react more slowly to the temperature change; however, even under those unlikely circumstances, the coil would eventually return to its original position as temperature equilibrium is reached. This return would make the thermostat ineffective. Incorrect Response B deals with the friction of two objects sliding across each other's surfaces. This phenomenon is not involved in the operation of a bimetallic-strip thermostat. Incorrect Response C deals with the density of materials. This characteristic is not pertinent to the operation of a bimetallic-strip thermostat.
58	Answer to question 58	A	Objective 007 When choosing materials for structural members of an aircraft, the two most important considerations are strength and weight (Correct Response A). The thrust of the motors and the long spans of the wings make strength critical in airplane design. At the same time, every extra pound translates into extra fuel usage since, unlike with land and sea vehicles, there is nothing but the power of the engines to support all of the weight. Plasticity (Incorrect Responses B and D) and elasticity (Incorrect Responses C and D) are also important factors to be taken into account; however, they do not rank as high in importance as strength and weight.
59	Answer to question 59	B	Objective 007 Because a triangle is the simplest geometric figure that will not change shape when the lengths of its sides are fixed (due to the side-side-side theorem of congruent triangles), the triangle is the basic structural unit of a truss bridge (Correct Response B). Circles (Incorrect Response A) and cylinders (Incorrect Response D) can also be very stable shapes, but they do not lend themselves as well to truss constructions, which typically consist of a lattice of straight beams. Squares (Incorrect Response C) that are not reinforced by triangles result in bending forces at the nodes of the lattices due to the fact that their angles are not geometrically constrained; hence, they are not as stable as triangles.
60	Answer to question 60	B	Objective 008 The graph represents a load deformation curve, showing how the material deforms and fails as the load increases. At approximately 17 seconds, the beam suffers severe deformation, so at 19 seconds the beam is at residual deformation (Correct Response B). Elasticity (elastic region) (Incorrect Response A) occurs at the linear point of the curve, between 0 seconds and 5 seconds, approximately. The beam can only stabilize and return to its normal form while it is elastic form, so Response C is incorrect. At approximately 5 seconds, the beam will yield its strength. Deformation will not disappear after the load is removed and the beam bends (Incorrect Response D).
61	Answer to question 61	D	Objective 008 A dead load (Correct Response D) is permanent, such as the weight of the structure or beam in a structure. Snow and wind loads (Incorrect Responses A and B) change over time: A snow load is not permanent and would be considered a live load, and wind effects vary with location and weather. Live loads (Incorrect Response C) are temporary, such as the people who come and go from the structure.
62	Answer to question 62	D	Objective 008 According to standard construction terminology, the long horizontal boards that support the subfloor are called joists (Correct Response D). Risers (Incorrect Response A) are the vertical components, sometimes called kickboards, that support the treads that people stand on while climbing the stairs. Some designs do not include risers. These are called open-riser stairs. Stringers (Incorrect Response B) are the diagonal support boards that run from the top to the bottom of a stair. Stair treads and risers are attached to the stringers. Studs (Incorrect Response C) are the vertical boards that are contained within walls to provide structural support.
63	Answer to question 63	C	Objective 008 The load pictured in the diagram will be transferred as tension forces in members A and B (Incorrect Responses A and B). The load will also be transferred as a bending force on member D; hence, the top surface of member D will be in compression and the bottom surface will be in tension (Incorrect Response D). The only labeled member that will experience pure compression will be member C (Correct Response C), which will be pushed together as the two support columns are angled inward.
64	Answer to question 64	A	Objective 008 Any downward load (weight) on the horizontal member (the beam) will create a tendency for it to pivot clockwise around the point where the underside of the beam meets the outer surface of the wall. Hence, a downward force on the exposed part of the beam will cause an upward force on the portion of the beam that is embedded in the wall. This will result in a compression force applied to the wall at point X (Correct Response A). One could argue that the top surface of the beam will have a tendency to slide out of the notch in the wall as the beam rotates clockwise. If the joint was glued or even if there was appreciable friction, this could lead to forces of tension (Incorrect Response B) and shear (Incorrect Response C) at point X. But these would be due to the resulting displacement of the beam. The primary static force would still be compression even if there were no actual movement. There is no torsion (i.e., twisting) (Incorrect Response D) force at point X.
65	Answer to question 65	B	Objective 008 The live load is any load applied to a building that is not due to the weight of the building and its designed components. This typically includes loads attributable to outside forces such as weather or loads during use such as the weight of people and furniture. The weight of accumulated snow (Correct Response B) is a typical example of a live load. The weight of air-conditioning units (Incorrect Response A), roof trusses (Incorrect Response C), and structural members (Incorrect Response D) are all examples of dead loads since they are due to the weight of the building and its designed components.
66	Answer to question 66	A	Objective 008 The top of the column is being pushed downward with a force of 600 N by the piece of metal. The top of the column is also being pulled upward with a force of 25 N by the line from the winch. The resultant combined force on the top of the column is ( negative 600 N) + (25 N) = ( negative 575 N), where the ( negative ) sign indicates a downward force. Since the 575 N force is directed downward on the top of the column, the resultant force is a compression force of 575 N (Correct Response A). Responses B and D are incorrectly reached by failing to realize that the net downward force on the top of the column will result in compression, not tension. Responses C and D are incorrectly reached by adding the magnitudes of the two forces. Since the forces act in opposite directions, the net force is found through subtraction with the resulting direction being determined by the force with the larger magnitude.
67	Answer to question 67	A	Objective 009 Linkage systems are used to manage forces and movement with the goal of obtaining ideal movement. Keeping the tires perpendicular to the road surface (Correct Response A) will keep the tires from wearing unevenly and decrease the force on the vehicle. Response B is incorrect because this system provides flexibility for the wheels, not strength to the vehicle itself. Response C is incorrect because the wheels will still move, but they will move in a perpendicular motion. Response D is incorrect because additional linkages in a complex linkage system will increase the cost, not reduce the cost.
68	Answer to question 68	D	Objective 009 Shock absorbers are used to arrest the movement of springs in both directions. Response D is correct because shock absorbers keep the spring from bouncing too far in a particular direction, helping the oscillation of the spring to die out. While a shock absorber helps keep tires planted on the ground, limiting travel (Incorrect Response A) is not the most important action between the shock and the spring. In the picture, when the linkage is compressed, the shock and spring absorb the motion, not the opposite (Incorrect Response B). It is the struts, not the shocks, that support the weight of a vehicle (Incorrect Response C).
69	Answer to question 69	C	Objective 009 The rudder on the stern (rear) of a ship steers the ship by deflecting the stern to the left or the right; however, this deflection depends on water flowing past the rudder. As the ship slows to a stop, the rudder becomes less and less effective for steering. When maneuvering a large ship up to a dock, side-mounted bow thrusters allow the bow (front) of the ship to be moved to the left or the right even when there is little or no forward motion (Correct Response C). However, in most situations, minor directional adjustments (Incorrect Response B) are best made using the rudder. Bow thrusters use fuel when they are operating (Incorrect Response A); this is in addition to the fuel used when steering with a rudder. When on a relatively steady course such as a computer-controlled course (Incorrect Response D), the rudder is the steering tool of choice.
70	Answer to question 70	C	Objective 009 Weight reduction is a paramount goal in rocket design. It takes a massive amount of energy to escape the earth's gravitational pull, and any reduction in weight significantly reduces the amount of fuel required for the rocket to reach orbit. Therefore, once the lower stages have accomplished their tasks, they are jettisoned for weight savings. Without such a multistage system, empty fuel storage containers would weigh down the rocket for no reason (Correct Response C). Response A is incorrect because once empty, the lower stages only serve to reduce efficiency until they are jettisoned. Reuse of jettisoned stages (Incorrect Response B) reduces cost associated with multistaging, but is not the primary reason for multistaging. Response D is incorrect because once a stage separates from the rocket, it can no longer provide additional thrust.
71	Answer to question 71	C	Objective 009 Automotive starters most commonly consist of a simple DC brushed motor with a retractable drive gear that pops out when the starter is engaged (Correct Response C). Because most automotive electrical systems use 12 volts DC, it does not make sense to use an A C motor such as an A C induction motor (Incorrect Response A) or an A C synchronous motor (Incorrect Response B). Even if the system were A C , it would be highly unlikely that something as sophisticated as a synchronous motor would be used. A DC stepper motor (Incorrect Response D) would not make sense for this application since these are designed for situations where the exact rotational angle of the motor can be controlled precisely. For a starter, a motor that simply spins when energized is all that is needed.
72	Answer to question 72	D	Objective 009 Intermodal freight transport is a term for transporting the same shipment of freight using several different modes such as on boats, trucks, and trains. Rather than load and unload the individual crates of freight from one vehicle to the next, they can all be packed into one large universal container that can then be stacked on a large ship, attached to a special railroad car, or converted into a truck trailer. This system drastically minimizes freight handling (Correct Response D). While this added efficiency could reduce delivery time (Incorrect Response A), this is not the primary motivation. The use of containers does not usually reduce overall weight (Incorrect Response B), and hence fuel consumption (Incorrect Response C). On the contrary, it could even increase weight since the container itself needs to be extremely rugged.
73	Answer to question 73	C	Objective 009 One common form of an automobile steering system is the rack-and-pinion system (Correct Response C). In this type of steering system, a small round gear on the end of the steering column engages a long flat-toothed rack gear. This system converts the rotational motion of the steering column to the linear motion of the rack. As the car is steered, the rack moves to the left and to the right. Linkages from the rack pivot the front wheels to steer the car. Rack-and-pinion gears are not commonly used in the support (Incorrect Response A), suspension (Incorrect Response B), or braking (Incorrect Response D) systems.
74	Answer to question 74	A	Objective 010 Hydraulic systems are used in projects requiring heavy-duty tools and equipment, such as large vehicles, while pneumatic systems handle smaller jobs with less power demand, such as small tools. Because hydraulics are used in major systems, the output required would need to be quick and highly responsive (Correct Response A). Incorrect Responses B and D pertain to pneumatic systems since pneumatics are used for smaller, lighter systems and since they produce limited power. Incorrect Response C pertains to both hydraulic and pneumatic systems, depending on the amount of force needed. Pneumatics are used with medium force and hydraulics with high force at low speeds.
75	Answer to question 75	D	Objective 010 The air receiver tank reduces cycling of the compressor, which helps increase efficiency, minimizing loss of energy and maintenance costs (Correct Response D). Response A is incorrect because high-pressure variations are not desirable; therefore, the tank guards against pressure variations, reducing high pressure as this increases energy use and wear and tear on the system. Responses B and C are correct as the tank does cool the air helping separate moisture; however, achieving efficiency in supplying compressed air is the primary goal.
76	Answer to question 76	D	Objective 010 The flow rate continuity equation states that the flow rate through a system remains constant. Flow rate is calculated by multiplying fluid velocity by cross-sectional area: A sub 1 times V sub 1 equals A sub 2 times V sub 2 where area times velocity at point 1 equals area times velocity at point 2 (Correct Response D). Since air is not lost through the duct, there is mass conservation remaining constant. However, Response A is incorrect because the volume flow rate equals the mass flow rate multiplied, not divided, by the volume flow rate at the exit. In a duct system, air can be treated as incompressible because pressure changes are small enough to disregard changes in density (Incorrect Response B). As air advances, the air in a smaller duct moves farther than the air in a larger duct, so the velocity in the smaller duct is higher (Incorrect Response C).
77	Answer to question 77	A	Objective 010 The system described in Correct Response A satisfies the requirements of the question. The system is open since the water is not recirculated, the system is geothermal since the hot springs are naturally heated by Earth's internal temperature, and the system involves a heat pump in the form of a refrigerant that is compressed to a liquid and allowed to expand to gas in an evaporator coil. Incorrect Response B is not primarily powered by geothermal energy, and it does not involve a heat pump. Incorrect Response C is not an open system, and it does not involve a heat pump. Incorrect Response D does not involve a heat pump.
78	Answer to question 78	C	Objective 010 A regulator consists of a valve that is controlled by a spring-loaded diaphragm to meter out the amount of gas necessary to maintain a preset outlet pressure that is lower than the inlet pressure (Correct Response C). Expanders (Incorrect Response A) and reducers (Incorrect Response B) adapt between different diameters of lines; while they may have some effect on line pressure at very high flow rates, they are not commonly used for this purpose. A decompression valve (Incorrect Response D) is an emergency pressure relief valve designed to avoid overpressure situations; it is not used to reduce line pressure under normal conditions.
79	Answer to question 79	C	Objective 010 Any bend in a fluid-carrying line will cause an increase in flow resistance (Correct Response C). The fact that the bend is in the downward direction will have no effect unless it implies a lowering of the altitude of the outlet when the outlet is open to atmospheric pressure; therefore, Response A is incorrect. Incorrect Responses B and D describe the relationship between laminar and turbulent flow: In real-world water plumbing situations, laminar flow is nearly impossible, and turbulent flow is the norm regardless of bends in the pipe. Laminar flow is more common with more viscous fluids flowing at low speeds through narrow pipes.
80	Answer to question 80	D	Objective 010 Conservation of matter and the relative incompressibility of fluids imply that the volume flow rate is equal at all points along the path of the fluid. This means that the velocity of the fluid must be greater in the narrower section of the tube. According to Bernoulli's principle, the pressure must be lower at points where the velocity is greater. This would result in a condition where the center column is lower than the two outer columns (Correct Response D) since the fluid in the center has less pressure to force the column up against atmospheric pressure. The two outer columns would be equal to each other since those regions of the tube have equal cross-sectional area, which would lead to equal velocity and hence equal pressure. Incorrect Response A assumes that there would be continuous reduction in pressure from the input to the output. While it is true that there would be no flow without some pressure differential from left to right in the diagram, that differential would be expected to be extremely small when compared to the pressure drop caused by the narrowing of the passage in the diagram. Incorrect Response B comes from assuming that the pressure is essentially equal throughout the horizontal path. This would only be correct if there were no flow to create the Bernoulli effect in the narrow portion of the tube. Incorrect Response C is reached by the intuitive misconception that the narrowing of a passage causes an increase in pressure.
81	Answer to question 81	D	Objective 011 The smaller warehouse is 4,800 cubic feet 20 feet by 20 feet by 12 feet , while the larger warehouse is 38,400 cubic feet 40 feet by 40 feet by 24 feet . Dividing 38,400 by 4,800 gives 8 as a result, so the larger warehouse is eight times larger. Therefore, the equation would be 8.00 times ten to the fourth power (Correct Response D). Incorrect Response A assumes the larger warehouse is twice as large since each side of the warehouse doubles in size; however, it does not consider the volume of the structure. Incorrect Response B considers only the area of the width and depth of each warehouse, multiplying 20 times 20 for 400 feet squared and 40 times 40 for 1,600 feet squared. Dividing 1,600 by 40 would make the warehouse 4 times as large, but this is incorrect as it does not consider the height of the building. Incorrect Response C does not follow from the given values.
82	Answer to question 82	D	Objective 011 Transparent sheathing should allow ultraviolet light from the sun to pass as it enhances the photosynthesis process of a plant; however, overheating can stress a plant causing leaves to curl and turn brown. Therefore, reflective materials should be used for the infrared spectrum to reduce the temperature of the greenhouse (Correct Response D). Incorrect Responses A, B, and D do not reflect both circumstances.
83	Answer to question 83	A	Objective 011 Thermostats are temperature-actuated switches. The more precise the temperature requirement, the more often the switch will trigger to turn the system on or off (Correct Response A). Response B is incorrect because the switch would trigger less frequently with a wider temperature range, as the device would only cycle the system on or off when the temperature is out of range. The time a system runs, less or more, would depend on the time it takes the system to reach the desired temperature range; time is not a function of the thermostat; therefore, Responses C and D are incorrect.
84	Answer to question 84	A	Objective 011 Energy is transferred by radiation when electromagnetic fields, mostly in the infrared part of the spectrum, exert forces on the electric charges in molecules or atoms, causing them to move more rapidly. This movement is perceived as heat and is a transfer of energy from the hotter body to the colder body. A prime example of this phenomenon is the radiant heat that is emitted by the Sun warming up the surface of a rockface on the Earth (Correct Response A). Incorrect Response B describes the mechanical transfer of energy from the moving air to the bird, and the convection transfer of energy from the heated rock to the air. Incorrect Response C describes the conduction transfer of energy from the rock to the adjoining soil. Incorrect Response D describes the chemical transfer of energy as the bird utilizes the stored energy from its food.
85	Answer to question 85	A	Objective 011 A heat pump forces heat to flow from a cold space to a hot space. In this example, the heat pump is forcing heat to flow between the outdoors and an indoor space. There is a theoretical limit to efficiency of any heat pump, which is defined as T sub H divided by the quantity T sub H minus T sub C where T sub H and T sub C are the temperatures of the hot and the cold spaces, respectively, as measured in the Kelvin scale. As T sub C gets smaller (for example, falling below freezing), the difference T sub H minus T sub C gets larger (approximately 22 K between a heated house interior and freezing), and the theoretical efficiency limit T sub H divided by the quantity T sub H minus T sub C gets smaller, most likely causing the heat pump to become inefficient (Correct Response A). This is why it would be better for the heat pump to pull its heat from the more thermally stable earth than from the ambient air. For Incorrect Response B, the heat pump will need to work in reverse to move energy from the interior living space to the warmer exterior. In this case, the difference T sub H minus T sub C would be much smaller (approximately 10 K between an air-conditioned interior space and 90°), implying more than double the theoretical efficiency limit. For Incorrect Responses C and D, the difference T sub H minus T sub C would be even smaller (approximately 5.6 K), implying an even higher theoretical efficiency limit.
86	Answer to question 86	B	Objective 011 The most commonly used fuel cells chemically combine hydrogen with oxygen. Instead of producing only thermal energy, which is generated when hydrogen undergoes combustion with oxygen, the reaction is modified to produce mostly electrical energy. The electrical energy can then be used to perform useful work. The combination of hydrogen and oxygen also produces water ( H 2 O ), which is an output of this process (Correct Response B). Hydrogen (Incorrect Response A) is an input for a fuel cell. Carbon dioxide (Incorrect Response C) is an output for the combustion of carbon in oxygen, not hydrogen, and is produced whenever fossil fuels are used. Methane (Incorrect Response D) is a hydrocarbon gas that is the primary component of natural gas, and it is often used as an input for internal combustion engines.
87	Answer to question 87	C	Objective 012 Alternating current can travel longer distances with lower energy losses than direct current. It is easier and cheaper to create enough power to transmit longer distances than direct current (Correct Response C). Response A is incorrect because the amount of electricity sent to the grid must equal the amount of electricity used. Response B is incorrect because high voltages would be needed for the grid network. Response D is incorrect because frequency will change with the type of wire used.
88	Answer to question 88	B	Objective 012 While adding a resistor will protect the component against power surges and regulate current (Incorrect Responses C and D), the main purpose for adding a resistor is to ensure that an electrical component receives the correct voltage (Correct Response B), preventing damage to the component. Response A is incorrect because inductance is inversely proportional to resistance.
89	Answer to question 89	A	Objective 012 The inverse square proportionality relationship described in the problem can be written symbolically as R = C divided by D Squared where R represents the resistance, C is a constant, and D represents the diameter. Therefore, 8 Ohms equals C divided by Y squared and R sub f equals C divided by the quantity 2 Y squared . Solving both equations for C and setting them equal yields 8 ohms times Y squared equals R sub f times 4 times Y squared . Solving this equation yields R sub f equals 2 ohms . In general, in an inverse square proportionality relationship, when a factor (in this case 2) is multiplied by the independent value, the dependent value is divided by the square of that factor (in this case 4) (Correct Response A). Incorrect Response B assumes that the resistance of a copper wire is a constant. While the resistivity of copper is a constant property of the material, resistance is dependent on resistivity, the cross-sectional area, and the length of the wire. Incorrect Response C assumes that the resistance is doubled when the diameter of the wire is doubled. Incorrect Response D assumes that resistance is squared when the diameter of the wire is doubled.
90	Answer to question 90	A	Objective 012 When a fuel source, like hydrogen, is fed into the anode, it comes in contact with a catalyst that causes separation of the atoms (Correct Response A). Protons migrate through the electrolyte (Incorrect Response C), to the cathode (Incorrect Response B), where they reunite with oxygen. For Incorrect Response D, the load is the current or electron flow through an external circuit.
91	Answer to question 91	D	Objective 012 The amount of mass that the electromagnet can lift depends on the magnetic field induced by the coil (which is proportional to the current and the number of windings) and on the magnetic properties of the core. Correct Response D would increase the mass that the electromagnet can lift since it involves increasing the number of windings. Incorrect Response A would not change the average lifting power (assuming that the 12-volt A C rating is measured as RMS voltage), though there would be a minor loss of power resulting from the constantly changing dipole alignment in the core. Incorrect Response B would result in little or no noticeable change in the performance of the magnet. The increase in the length of wire causing a decrease in current would probably outweigh the decrease in reluctance (magnetic resistance) of the thicker bar. Incorrect Response C would result in a major reduction in lifting ability since copper is a far less magnetic substance than iron.
92	Answer to question 92	D	Objective 012 The input and output voltages of a transformer can be calculated using the equation V sub I divided by N sub I equals V sub O divided by N sub O where V and N represent the voltage and the number of windings respectively, and the subscripts _i and _o represent input and output respectively. In this case, 220 volts divided by 1.5 times 10 to the second power equals V sub 0 divided by 4.5 times ten to the second power . Solving this equation yields V sub O = 660 V (Correct Response D). Incorrect Response A is reached by using the formula V sub I divided by N sub O equals V sub O divided by N sub I , or 220 volts divided by 4.5 times 10 to the second power equals V sub 0 divided by 1.5 times ten to the second power , resulting in V sub O = 73.3 V. Incorrect Response B is reached by assuming the output voltage is always half the input voltage. Incorrect Response C comes from assuming that the output voltage is always double the input voltage.
93	Answer to question 93	A	Objective 012 In order to measure current with a standard multimeter, the multimeter must first be set to ammeter mode. Next, the circuit must be broken at a point through which the unknown current is flowing. Then the circuit is reconnected so that the unknown current flows into one lead of the multimeter and out the other lead, effectively wiring the multimeter in series with the circuit. Because the multimeter has very low impedance when set to ammeter mode, the circuit should not be affected by its inclusion. Correct Response A is an example of such a connection where the circuit is broken between wire X and the negative terminal. Since all of the current flowing through the lamp also flows though wire X, and now through the multimeter, the correct current will be measured. Incorrect Responses B, C, and D all involve short-circuiting the lamp. This will result in blowing the fuse in the multimeter or burning out the ammeter mode if there is no fuse.
94	Answer to question 94	B	Objective 013 This is a demonstration of Pascal’s principle. Within a closed system, any change in pressure in one part of the system is transmitted without loss to the fluid throughout the container. So the pressure, the force applied divided by the cross-sectional area of the small piston, produces an equal increase in pressure on the large piston. The formula for Pascal’s principle is F = P A . Since P sub I equals P sub O, F sub I divided by A sub I equals F sub O divided by A sub O . The formula for area is pie r squared . Since radius is squared and the mechanical advantage is 9, then 3 squared = 9, meaning the radius has to be 3 times larger. If the original radius is 2, then the larger piston needs a radius of 3 times 2 or 6 cm (Correct Response B). Response A is incorrect because the piston area is 3 times as large, not 3 cm. Incorrect Response D indicates that the radius of 2 is multiplied by the mechanical advantage of 9. Incorrect Response C is the mechanical advantage of 9 less 2 cm.
95	Answer to question 95	C	Objective 013 This is an example of an Atwood’s machine. When mass is on both sides of a pulley, the motor has to lift only the difference in mass. This allows the motor to exert minimal effort when the elevator car is at rest or when it needs to accelerate (Correct Response C). Response A is incorrect because a larger elevator would require a large motor or counterweight. Response B is incorrect because greater speed would require more acceleration, which is a function of the motor. Response D is incorrect because brakes are needed to achieve rest from acceleration.
96	Answer to question 96	D	Objective 013 The worm gear looks like a screw, while the spur gear looks like a wheel. The worm is always the driving gear (Correct Response D). The opposite configuration would not work as the rotational power is applied to the worm, while the wheel is pushed against the load. The worm is butted up against the spur gear in a perpendicular position and, therefore, the components are not parallel (Incorrect Response A). The spur wheel has more “teeth” than a worm gear and, therefore, the spur wheel will turn more slowly than the worm (Incorrect Response B). While the driving gear transmits force applied to the output gear, the amount of torque at the axle will depend on the function of the gears (Incorrect Response C). The purpose could be to increase speed and decrease torque or the opposite.
97	Answer to question 97	B	Objective 013 Due to conservation of mechanical energy, any kinetic energy gained by the rock will have to be equal to any loss of gravitational potential energy. Since the rock started at rest, it can be assumed that the final kinetic energy is equal to the initial gravitational potential energy due to the rock’s height relative to the ground. The gravitational potential energy can be calculated as GPE = mgh, where GPE represents gravitational potential energy, m represents mass, g represents acceleration due to gravity (9.8 meters per second squared ), and h represents the height of the rock above the ground. Therefore, the final kinetic energy equals the initial gravitational potential energy or 64 kilograms times 9.8 meters per second squared times 20 meters = 12,544 J (Correct Response B). Incorrect Response A comes from using the incorrect formula as GPE = gh square root of m = 1,568 J. Incorrect Response C is reached from the formula GPE = g squared h square root of m = 15,366 J. Incorrect Response D comes from the formula as GPE = m g squared h = 122,931 J.
98	Answer to question 98	C	Objective 013 In pulley and belt systems as well as in gear systems, pulleys and gears with smaller diameters rotate faster than those with larger diameters. In pulley and belt systems, where the belt is not twisted or made to cross itself (as in a figure-8 pattern), all pulleys rotate in the same direction. In a gear system, adjacent gears rotate in opposite directions. In Correct Response C, the output pulley has the smaller diameter, which means that it will rotate faster than the input pulley. Since it is a simple pulley and belt system, both shafts rotate in the same direction. In Incorrect Responses A and B, the output shaft rotates slower than the input shaft. In Incorrect Response D, the output shaft rotates slower and in the opposite direction of the input shaft.
99	Answer to question 99	A	Objective 013 Torque is calculated as T = F times r where T represents torque, F represents force, and r represents radius. In the case of a belt and pulley system, both pulleys experience the same force as applied by or to the belt. Hence, if we solve for F and set F equal for both pulleys, we get T sub I divided by r sub I equals t sub O divided by r sub O . Therefore, 195 Nm divided by 9 inches equals T sub O divided by 3 inches Solving for T sub O yields T sub O equals 65.0 Newton meters (Correct Response A). Incorrect Response B assumes that the torque would be cut in half, and Incorrect Response C assumes that the torque would be doubled. Incorrect Response D comes from using the formula T sub I divided by r sub O equals T sub O divided by R sub I or 195 Newton meters divided by 3 inches equals T sub O divided by 9 inches to get T sub O equals 585 Newton meters .
100	Answer to question 100	B	Objective 013 In order for the seesaw to be balanced, the torques must sum to zero. Torque is force times lever arm length. The force is the weight, which is the product of mass and the acceleration of gravity. Therefore, 90 kilograms times 9.8 meters per second squared times 10 feet minus the quantity W sub A times 9.8 meters per second squared times 6 feet = 0 where W sub a represents the weight of the adult. Solving this equation yields W sub a = 150 kg (Correct Response B). Responses A, C, and D are incorrect and do not follow from the given values.
Total Correct:	Total Correct	Review your results against the test objectives.

Open Responses, Sample Responses, and Analyses

Question Number	Your Response Read about how your responses are scored and how to evaluate your practice responses
101	Answer to 101 Open Response Item Assignment #1 For each assignment, you may type your written response on the assigned topic in the box provided. Essay Response Field
First Sample Weak Response (show sample responsehide sample response)	First Sample Weak Response to Open-Response Item Assignment #1 The problem here is how to design a movie screen to show outdoor movies on. I would have the students brainstorm ideas by looking at movie screens online and deciding what materials they want to work with - metal, wood, plastic, etc. They would sketch their designs and then everybody could look at the designs and then comment. To test the screens we could take all the screens outside and project a movie onto them and see how they perform. We could watch a movie about the engineering design process, like the movie where they design a shopping cart, and then talk about how the design process of their shopping cart is like the design process of our movie screen. A science and engineering practice is constructing explanations and designing solutions. The students would have to design a solution to the problem of the movie screen and explain to the teacher (me) why it was a good solution. I would have the students search online for materials they would like to use in their movie screens. Some of these materials might be too expensive. If any materials had to be cut, I would stop the class to give a demonstration on the proper use of all the different kinds of saws.
First Weak Response Analysis (show response analysishide response analysis)	Analysis of First Weak Response to Open-Response Item Assignment #1 This is an example of a weak response because it is characterized by the following: Purpose: The purpose of the assignment is partially achieved. The first paragraph describes how the candidate would support students in applying the engineering design process. Some of these steps only half meet the purpose. For example, the candidate defines the problem rather than describing how to help the students define the problem. The second paragraph identifies a science and engineering practice but does little to describe how it could be used to help the students. The third paragraph vaguely addresses materials and only briefly addresses tools, processes, and safety. Subject Matter Knowledge: There is a limited, possibly inaccurate or inappropriate, application of subject matter knowledge. The candidate conflates the brainstorming and research phases of the engineering design process. Apart from that, nothing in this response is strictly inaccurate. Limitations in subject matter knowledge are largely matters of poor reasoning. Support: The supporting evidence is limited; there are few relevant examples. The first paragraph provides some relevant examples but just as often fails to provide them. The description of the testing does not specify what the screens are being tested for and only vaguely describes the procedure. The lesson in the second paragraph gives little sense of any procedure and includes no examples of solutions the students might design or explanations they might give. The third paragraph offers no examples of materials, no examples of kinds of saws, and no description of what a safety demonstration might include. Rationale: The response reflects a limited, poorly reasoned understanding of the topic. Although the first paragraph walks through some of the steps of the engineering design process, it leaves us with questions. Why are the students basing their designs on “materials they want to work with” rather than on materials that fit the criteria and constraints? Are the students sketching multiple designs or only one? The third paragraph leaves us with similar questions. Why is the teacher stopping the class rather than giving the demonstration at the beginning? Is there a need to give a demonstration on “all the different kinds of saws” if only one kind of saw is called for?
Second Sample Weak Response (show sample responsehide sample response)	Second Sample Weak Response to Open-Response Item Assignment #1 I would have the students apply the engineering design process to prototype a solution in the classroom. They would have to build a prototype of the movie screen that could be tested and evaluated to see if it met the criteria and constraints. There would have to be some very specific kinds of tests it went through so that you knew what you were testing for. Students would have to collect data on how the movie screen performed. If the screen failed to meet criteria and constraints I would send the students back to the drawing board, literally because they would have to sketch new designs that solved the problems and then choose the best design to prototype. If that prototype failed to meet criteria and constraints you would have to go back and redesign again in an iterative process. A key science and engineering practice is redesign. After you test the prototype, if it doesn’t work, you go back and redesign in order to fix the problem. I would do this with the students if they built the movie screen and it didn’t work. They would have to figure out what was wrong with it, redesign and then test again. Materials would depend on the students’ design. They could include wood, metal, plastic, and different types of fabric. Tools would also depend on the students’ design. They could include screwdrivers, wrenches, drills, as well as different kinds of cutting tools. All students would be required to adhere to my directions and to safety procedures posted around the classroom.
Second Weak Response Analysis (show response analysishide response analysis)	Analysis of Second Weak Response to Open-Response Item Assignment #1 This is an example of a weak response because it is characterized by the following: Purpose: The purpose of the assignment is partially achieved. The first paragraph only generally describes how the students would be supported in applying some of the steps of the design process; there is no specific application to the movie screen project. The second paragraph fails to identify a science and engineering practice. The third paragraph presents possible materials and tools, though there is no description of guiding the students through this project specifically. Safety considerations are mentioned, but again, without any specific application to the movie screen. Subject Matter Knowledge: There is a limited, possibly inaccurate or inappropriate, application of subject matter knowledge. The response demonstrates some knowledge of the engineering design process in its references to criteria and constraints and the iterative nature of the EDP. This knowledge, however, is not applied to the problem at hand. The second paragraph contains an obvious inaccuracy. What the candidate says about redesign is true in a general way, but redesign is a step in the engineering design process, not one of the eight science and engineering practices. Support: The supporting evidence is limited; there are few relevant examples. This response is seriously limited by a lack of specific examples applicable to the movie screen project. In the first paragraph, for example, what are the criteria and constraints? What kinds of tests would be performed? What kind of data would be collected? The second paragraph presents no hypothetical example of a failed prototype or a procedure for redesign. The third paragraph presents not a single specific safety procedure. Rationale: The response reflects a limited, poorly reasoned understanding of the topic. Although the third paragraph presents what looks like specific support, no rationale is offered for any of it. The candidate has not proposed any specific approach to the movie screen problem, so all of these proposed materials, tools, and safety procedures remain mere potentialities. There is no way to guide the students in selecting them.
First Sample Strong Response (show sample responsehide sample response)	First Sample Strong Response to Open-Response Item Assignment #1 A science and engineering practice related to this problem is Asking Questions and Defining Problems. In order to design a successful solution, the problem needs to be clearly defined. The prompt states only that the screen must be lightweight and portable, but students should be encouraged to consider the implied criteria and constraints. The screen will be outdoors, so it should be big enough to see from a distance and able to withstand some wind and rain. Any assembly required should be manageable by students without specialized knowledge or tools. It may be smart to make it foldable or collapsible so it can be stored easily. Cost is another constraint. A school club may not have the funds for commercial movie screen material. Defining problems is also the first step of the engineering design process: a clear understanding of the problem would focus the students’ research and selection of materials and drive them to generate multiple solutions that would satisfy the criteria and constraints. Although I would allow the students to choose their own best solution, I would encourage them to pursue their riskiest, most innovative solutions, rather than the easiest, most obvious ones. As we advanced to the prototype stage, the more innovative solutions might require additional research into materials and material properties, but this is in keeping with the iterative nature of the engineering design process. Some tools and processes may require safety instruction - always use safety glasses while hammering metal, for example, and don’t cut metal with a wood saw. Finally, although not specifically mentioned as a criterion or constraint, the idea of an outdoor movie night might steer us toward “green construction” - materials that are recycled, biodegradable, or locally sourced. Students could be encouraged to research commercially available reusable fasteners like silicone zip ties and Velcro made from recycled materials. Who knows - maybe a plant-based movie screen?
First Strong Response Analysis (show response analysishide response analysis)	Analysis of First Strong Response to Open-Response Item Assignment #1 This is an example of a strong response because it is characterized by the following: Purpose: The purpose of the assignment is fully achieved. In the first paragraph, the candidate identifies a science and engineering practice and describes, by proposing several criteria and constraints, how students might use that practice to design the movie screen. The second paragraph presents a general overview of the way in which the candidate would support students through the engineering design process, paying detailed attention to one step in particular: choosing the best solution. In the third paragraph, the candidate touches briefly on tools, processes, and safety while developing materials more fully with several examples. Subject Matter Knowledge: There is a substantial, accurate, and appropriate application of subject matter knowledge. The candidate correctly identifies and applies one of the eight science and engineering practices and identifies and understands the function of the steps in the engineering design process. The candidate also demonstrates knowledge of relevant safety measures and appropriately applies a knowledge of green construction. Support: The supporting evidence is sound; there are high-quality, relevant examples. In the first paragraph, the candidate proposes a variety of specific considerations for the movie screen. In the third paragraph, the candidate proposes specific safety precautions and several types of “green” materials as well as specific “green” products. Rationale: The response reflects an ably reasoned, comprehensive understanding of the topic. The candidate has thought through the problem of the movie screen in depth, considering not only the explicit criteria and constraints but also some criteria and constraints implied by the context. The candidate also relates the science and engineering practice of Defining Problems to the “identify the problem” step of the engineering design process. Defining problems reappears in the third paragraph, as the candidate questions if any criteria are implied by the very notion of an outdoor movie night.
Second Sample Strong Response (show sample responsehide sample response)	Second Sample Strong Response to Open-Response Item Assignment #1 The engineering design process could be followed as a series of lessons with class time allotted to each step. On the first day, I would have students meet in small groups (their design teams) to generate questions they would need answered in order to establish criteria and constraints. Who will set up the screen? How often will it be used? What is the budget and timeline for the project? I would arrange for a Q&A session with a representative from the school club (the client). Next, students would research commercial movie screens and DIY solutions on the internet, as well as catalogues of materials suppliers. Once they generated multiple solutions to the problem and chose the best one, each group would submit a parts list in keeping with the budget. Subsequent lessons would be given to prototyping, testing, communicating the results, and revising the design if necessary. To help them design a solution, students could utilize the science and engineering practice of “developing and using models.” They might want to model a particular fabric, support, or fastener before committing to it in a full-scale prototype. A model of the screen could be tested to see how much wind it could withstand before tipping over. A model of the screen could also be presented to the client during the “communicating results” step of the engineering design process. Tools and materials would depend on the nature of the prototype and the resources available in the classroom. Wood construction might require carpentry tools and skills, while a metal design could require facility in the use of different fasteners (clamps, nuts/bolts, grommets, velcro). Constructing the prototype might entail measuring, cutting, drilling, or welding. If you had to climb a ladder to fix the fabric, you might need safety measures like having someone hold the ladder. OSHA requires a safety harness if you’re more than six feet off the ground, which might be a good practice in this case.
Second Strong Response Analysis (show response analysishide response analysis)	Analysis of Second Strong Response to Open-Response Item Assignment #1 This is an example of a strong response because it is characterized by the following: Purpose: The purpose of the assignment is fully achieved. The first paragraph presents a general overview of the way in which the candidate would support students throughout the engineering design process, paying more detailed attention to two early steps, “identify the problem” and “research the problem.” The second paragraph identifies the science and engineering practice of Developing and Using Models and specifies three ways in which models could help the students design a solution. The third paragraph imagines a variety of approaches students might take toward materials, tools, and processes, providing representative specific examples (types of fasteners, ladder safety). Subject Matter Knowledge: There is a substantial, accurate, and appropriate application of subject matter knowledge. The candidate correctly identifies and applies one of the eight science and engineering practices and identifies and understands the function of the steps in the engineering design process. Subject matter knowledge is also evident in the comparison of small groups to “design teams” and in the distinction between commercial products and DIY solutions. While the safety harness may be an extreme precaution in this case, the candidate’s knowledge of OSHA requirements brings specificity and variety to the discussion of ladder safety. Support: The supporting evidence is sound; there are high-quality, relevant examples. The candidate imagines specific questions the students might ask as part of the engineering design process as well as specific sources to be consulted in their research. Examples given in the third paragraph (types of fasteners, ladder safety) are varied and specific. Rationale: The response reflects an ably reasoned, comprehensive understanding of the topic. The sequence of steps in the engineering design process is clearly marked (On the first day, Next, Once). In the second paragraph, the variety of uses the candidate proposes for models shows a comprehensive understanding of this science and engineering practice.
102	Answer to 102 Open-Response Item Assignment #2 For each assignment, you may type your written response on the assigned topic in the box provided. Essay Response Field
First Sample Weak Response (show sample responsehide sample response)	First Sample Weak Response to Open-Response Item Assignment #2 The expansion valve expands the refrigerant and makes it ready to pass through the evaporator coils, usually made of copper. They are heated by the outside air. Then the refrigerant evaporates, becoming gas. The gas then flows into the compressor, which compresses the gas down and makes it ready to pass through the condenser. Because the condenser is colder than the interior of the building, the heat is transferred into the building. The refrigerant is then funneled into the expansion valve to start the whole cycle over again. Thermal energy or heat is transferred from the outside air to the evaporator. The input is exterior heat and the output is a warmed evaporator which can warm the refrigerant and make it evaporate. Thermal energy is also transferred from the condenser to the interior of the building. The input is hot gas from the compressor and the output is warm air. A science and engineering practice that could help a student make sense of this system is developing and using models. You could have the students build a model of the heat pump to help them understand how thermal energy is transferred from a low heat source to a hotter interior space of a building.
First Weak Response Analysis (show response analysishide response analysis)	Analysis of First Weak Response to Open-Response Item Assignment #2 This is an example of a weak response because it is characterized by the following: Purpose: The purpose of the assignment is partially achieved. The first paragraph describes some of the functions and characteristics of each of the components. The second paragraph partially addresses the energy transfers. The third paragraph identifies the science and engineering practice of Developing and Using Models but does not describe how it could be used to help the students, beyond saying “have the students build a model." Subject Matter Knowledge: There is a limited, possibly inaccurate or inappropriate, application of subject matter knowledge. The first and second paragraphs contain a number of inaccuracies and ambiguities. What process is involved in the vague phrase “makes it ready”? The condenser is not colder than the interior of the building. What process is implied by the word “funneled”? The output of the evaporator is not “a warmed evaporator.” Support: The supporting evidence is limited; there are few relevant examples. The second paragraph does not describe the input and output of the expansion valve or the input to the compressor. The third paragraph provides little support in its description of how the practice of Developing and Using Models could be used to help students. Rationale: The response reflects a limited, poorly reasoned understanding of the topic. The first paragraph shows a partial understanding of the relationship between the pressure and the temperature of the refrigerant. The second paragraph shows a partial understanding of inputs and outputs. The third paragraph presents a highly impractical classroom exercise—building a model of a heat pump. The rationale given for this exercise is largely borrowed from the prompt.
Second Sample Weak Response (show sample responsehide sample response)	Second Sample Weak Response to Open-Response Item Assignment #2 A heat pump basically takes outside air and turns it into warm air to heat an interior of a house. Because there is both a compressor to turn the refrigerant warmer and an expansion valve to make it cooler, the heat pump can work as both a heating system or an air conditioner. Heat pumps are efficient ways of cooling or warming an environment because the cold air basically becomes the source of heat for your house or for your hot water. The compressor transfers heat into the refrigerant. The condenser transfers heat into the building. The expansion valve transfers the refrigerant to the evaporator. The evaporator transfers ambient heat into the refrigerant. A good practice to follow with a heat pump is regular maintenance. Students should understand that a heat pump should be serviced by a licensed technician once per year. There are filters that have to be replaced on a regular basis. There can also be buildup in the ducts that can cause the heat pump not to operate properly. That will lower the efficiency and ultimately cost you more on your electric bill.
Second Weak Response Analysis (show response analysishide response analysis)	Analysis of Second Weak Response to Open-Response Item Assignment #2 This is an example of a weak response because it is characterized by the following: Purpose: The purpose of the assignment is partially achieved. Although the first paragraph describes some of the functions (“takes outside air and turns it into warm air”) and characteristics (“can work as both a heating system or an air conditioner”) of the system as a whole, it does not describe the function or characteristics of each component. The first and last sentence of this paragraph are largely repetitive. The second paragraph describes energy transfers but does not include inputs and outputs. The third paragraph fails to identify a science and engineering practice. Subject Matter Knowledge: There is a limited, possibly inaccurate or inappropriate, application of subject matter knowledge. The most obvious inaccuracy in this response is in the third paragraph, where the candidate presents “regular maintenance” as a science and engineering practice. Limitations in subject matter knowledge are also evident in what is omitted from the response—for example, the inputs and outputs. The third “transfer” in the second paragraph (“The expansion valve transfers the refrigerant to the evaporator”) does not describe a transfer of energy. Support: The supporting evidence is limited; there are few relevant examples. The support is limited by what is omitted from the response—the characteristics and function of the components in the first paragraph and the inputs and outputs in the second paragraph. The information in the third paragraph may be largely true, but it is not relevant to the purpose of the assignment. Rationale: The response reflects a limited, poorly reasoned understanding of the topic. Again, a limited understanding of the topic is most evident in the third paragraph. Not only does the candidate fail to identify a science and engineering practice, but the pedagogical objective—to help students make sense of the system—seems to have been missed. The reason given in the first paragraph—that “the cold air basically becomes the source of heat for your house”—does not explain how a heat pump can cool an environment.
First Sample Strong Response (show sample responsehide sample response)	First Sample Strong Response to Open-Response Item Assignment #2 The compressor is an electrically-powered pump that makes the incoming refrigerant denser and hotter. It can then transfer warmth to the ambient interior air through the condenser coils. The refrigerant then passes through the expansion valve, which decompresses the refrigerant from the condenser, making it less dense and cooler. As the refrigerant enters the evaporator, which transfers the exterior ambient warmth to the refrigerant, it passes then again through the cycle, beginning again with the compressor. There are two forms of energy transfer in this system. First, the transfer of exterior warmth to the interior. The input of the system is exterior warmth, and the output is interior warmth. Second, the transfer of electrical energy to the compressor, which is used to further heat the refrigerant. The input to the compressor is electrical energy, and the output is the increased temperature of the refrigerant. A science and engineering process that could be used to help students make sense of this system is Constructing Explanations and Designing Solutions. I would conduct a lesson about the system to demonstrate that a compressor increases the temperature of the refrigerant, and that an expansion valve makes the refrigerant cooler. This could be done as direct instruction plus class discussion and include simple experiments. For example, one experiment is to puncture a C O 2 cartridge. As the C O 2 escapes, the temperature of the metal casing drops. This way the students can touch and feel the actual temperature difference. You could also measure the temperature with a non-contact laser thermometer. Have the students generate explanations as to why the cartridge dropped in temperature.
First Strong Response Analysis (show response analysishide response analysis)	Analysis of First Strong Response to Open-Response Item Assignment #2 This is an example of a strong response because it is characterized by the following: Purpose: The purpose of the assignment is fully achieved. The first paragraph describes some combination of the characteristics (“The compressor is an electrically-powered pump”) and the function (“that makes the incoming refrigerant denser and hotter”) of each of the components in the system. The second paragraph describes two forms of energy transfer, including inputs and outputs. The third paragraph identifies the science and engineering practice of Constructing Explanations and Designing Solutions and describes a classroom lesson in which students conduct an experiment and construct explanations of the results. Subject Matter Knowledge: There is a substantial, accurate, and appropriate application of subject matter knowledge in the candidate’s description of the components and energy transfers. The candidate identifies and applies one of the eight science and engineering practices, drawing an analogy between a heat pump and a C O 2 cartridge and designing an appropriate procedure to demonstrate the relation between pressure and temperature. Support: The supporting evidence is sound; there are high-quality, relevant examples, most notably the experiment in the third paragraph, which is described succinctly but with sufficient detail. The last sentence draws the relevance of the experiment to the science and engineering practice of Constructing Explanations. Rationale: The response reflects an ably reasoned, comprehensive understanding of the topic. The first paragraph methodically traces the refrigerant through each component in the system in a clockwise direction. Note also how the electricity that powers the compressor in the first paragraph leads to the inclusion of electricity in the energy transfers described in the second paragraph. This demonstrates a comprehensive understanding of the topic.
Second Sample Strong Response (show sample responsehide sample response)	Second Sample Strong Response to Open-Response Item Assignment #2 The refrigerant in the evaporator coils is raised to the ambient outdoor temperature being housed in an evaporator unit located outside the building. The refrigerant is pumped through the compressor, which reduces the volume of the refrigerant by increasing the pressure on it. In consequence, its temperature increases, because a liquid increases in temperature as it is compressed. As the refrigerant moves through the condenser coils, heat is conducted to the inside air in the building. As the refrigerant moves through the expansion valve, it returns to its less dense and cooler state. Then the cycle begins again - as the refrigerant moves through the evaporator, the evaporator coils conduct outside heat to it. If you run the process in reverse, you would be cooling the building. The input to the expansion valve is condensed refrigerant. The output is cooled refrigerant. The input to the evaporator coils is the cooled refrigerant, where the ambient air raises the temperature of the refrigerant. The warmed refrigerant is output to the compressor. The compressor takes in the refrigerant and compresses it, warming it further, then outputs it to the condenser coils, which transfer the heat to the inside air. Then the cycle begins again. The science and engineering practice of Analyzing and Interpreting Data can be used to help students understand this system. I would give the students a diagram like the one in the Exhibit, but that indicated the temperature of the outside air and the inside air, as well as the pressure levels and temperature of the refrigerant before it enters and after it leaves each component in the system. This diagram would provide data that reflect how the system functions. I would ask the students to examine those data points and identify patterns they see in the data. The students should conclude from the data that when the pressure increases, the temperature increases, and when the pressure decreases, the temperature decreases.
Second Strong Response Analysis (show response analysishide response analysis)	Analysis of Second Strong Response to Open-Response Item Assignment #2 This is an example of a strong response because it is characterized by the following: Purpose: The purpose of the assignment is fully achieved. The first paragraph describes the function of each of the components in the system, the characteristics of the refrigerant as it passes through each of those components, and some characteristics of the components themselves (“housed in an evaporator unit located outside the building”). The second paragraph describes energy transfers between each of the components. The third paragraph identifies a science and engineering practice and describes a relevant classroom lesson in which students analyze data to understand the system. Subject Matter Knowledge: There is a substantial, accurate, and appropriate application of subject matter knowledge in the candidate’s description of the components and energy transfers. The candidate identifies and applies one of the eight science and engineering practices, identifies physical processes (conduction), and applies physical laws (“a liquid increases in temperature as it is compressed”). Support: The supporting evidence is sound; there are high-quality, relevant examples, most notably the experiment in the third paragraph, which succinctly but with sufficient detail outlines a procedure, materials, and expected outcomes. Rationale: The response reflects an ably reasoned, comprehensive understanding of the topic. The first paragraph methodically traces the refrigerant through each component in the system in a clockwise direction, using transitional phrases to indicate relationships: In consequence, As the refrigerant moves through, Then the cycle begins again. The exercise in the third paragraph has been carefully thought through; the candidate has determined precisely what data would be necessary for such an exercise.
Review the Performance Characteristics and Score Scale for Written Performance Assignments.

Multiple Choice Question
Practice Test Evaluation Chart

In the evaluation chart that follows, the multiple-choice questions are arranged in numerical order and by test objective. Check your responses against the correct responses provided to determine how many questions within each objective you answered correctly.

Subarea 1 : Engineering Design

Objective 0001: Apply knowledge of connections between engineering, technology, mathematics, and natural sciences.

Question Number	Your Response	Correct Response
1		C
2		C
3		B
4		B
5		B
6		B
7		D
8		C

Total Correct for Objective 1 out of 8

Objective 0002: Apply knowledge of engineering design in developing technological solutions to problems within given specifications.

Question Number	Your Response	Correct Response
9		D
10		D
11		C
12		A
13		C
14		A
15		B
16		B

Total Correct for Objective 2 out of 8

Objective 0003: Apply knowledge of technology and engineering in social contexts.

Question Number	Your Response	Correct Response
17		C
18		B
19		A
20		D
21		B
22		A
23		C
24		B
25		A

Total Correct for Objective 3 out of 9

Subarea 1 (Objectives 0001–0003) Total Total Correct for Subarea 1 out of 25

Subarea 2 : Materials, Tools, and Manufacturing

Objective 0004: Apply knowledge of the selection and safe use of appropriate materials, tools, equipment, and machines in technology and engineering.

Question Number	Your Response	Correct Response
26		D
27		B
28		A
29		C
30		A
31		C
32		C
33		A
34		B
35		C

Total Correct for Objective 4 out of 10

Objective 0005: Apply knowledge of manufacturing processes used to create products that meet stated requirements.

Question Number	Your Response	Correct Response
36		D
38		C
39		C
40		B
41		A
42		D
43		A
44		D
45		B
46		C

Total Correct for Objective 5 out of 10

Subarea 2 (Objectives 0004–0005) Total Total Correct for Subarea 2 out of 20

Subarea 3 : Technological Systems

Objective 0006: Apply knowledge of processes used to communicate data and information.

Question Number	Your Response	Correct Response
47		D
48		C
49		B
50		D
51		B
52		D
53		A

Total Correct for Objective 6 out of 7

Objective 0007: Apply knowledge of design factors, material selection, and constraints in building structures.

Question Number	Your Response	Correct Response
37		A
54		B
55		A
56		B
57		D
58		A
59		B

Total Correct for Objective 7 out of 7

Objective 0008: Analyze the effects of forces in construction technology.

Question Number	Your Response	Correct Response
60		B
61		D
62		D
63		C
64		A
65		B
66		A

Total Correct for Objective 8 out of 7

Objective 0009: Apply knowledge of the principles and characteristics of transportation technology.

Question Number	Your Response	Correct Response
67		A
68		D
69		C
70		C
71		C
72		D
73		C

Total Correct for Objective 9 out of 7

Subarea 3 (Objectives 0006–0009) Total Total Correct for Subarea 3 out of 28

Subarea 4 : Energy and Power Technologies

Objective 0010: Apply knowledge of fluid systems and their role in technological systems.

Question Number	Your Response	Correct Response
74		A
75		D
76		D
77		A
78		C
79		C
80		D

Total Correct for Objective 10 out of 7

Objective 0011: Apply knowledge of thermal systems and their role in technological systems.

Question Number	Your Response	Correct Response
81		D
82		D
83		A
84		A
85		A
86		B

Total Correct for Objective 11 out of 6

Objective 0012: Apply knowledge of electrical principles and components and their roles in technological systems.

Question Number	Your Response	Correct Response
87		C
88		B
89		A
90		A
91		D
92		D
93		A

Total Correct for Objective 12 out of 7

Objective 0013: Apply knowledge of basic principles of energy, work, and power and their relationship to mechanical systems.

Question Number	Your Response	Correct Response
94		B
95		C
96		D
97		B
98		C
99		A
100		B

Total Correct for Objective 13 out of 7

Subarea 4 (Objectives 0010–0013) Total Total Correct for Subarea 4 out of 27

Practice Test Score Calculation

The practice test score calculation is provided so that you may better gauge your performance and degree of readiness to take an MTEL test at an operational administration. Although the results of this practice test may be used as one indicator of potential strengths and weaknesses in your knowledge of the content on the official test, it is not possible to predict precisely how you might score on an official MTEL test.

The Sample Responses and Analyses for the open-response items may help you determine whether your responses are more similar to the strong or weak samples. The Scoring Rubric can also assist in estimating a score for your open responses. You may also wish to ask a mentor or teacher to help evaluate your responses to the open-response questions prior to calculating your total estimated score.

How to Calculate Your Practice Test Score

Review the directions in the sample below and then use the blank practice test score calculation worksheet to calculate your estimated score.

Multiple-Choice Section

Enter the total number of multiple-choice questions you answered correctly:

Use Table 1 below to convert that number to the score and write your score in Box A:

197

Open-Response Section

Enter the number of points (1 to 4) for your first open-response question:

Enter the number of points (1 to 4) for your second open-response question:

Add those two numbers (Number of open-response question points):

Use Table 2 below to convert that number to the score and write your score in Box B:

Total Practice Test Score (Estimated MTEL Score)

Add the numbers in Boxes A and B for an estimate of your MTEL score:

A + B =

243

Practice Test Score Calculation Worksheet: Technology/Engineering (70)

Table 1:

Number of Multiple-Choice Questions Correct	Estimated MTEL Score
0 to 25	117
26 to 30	125
31 to 35	133
36 to 40	141
41 to 45	149
46 to 50	157
51 to 55	165
56 to 60	173
61 to 65	181
66 to 70	189
71 to 75	197
76 to 80	205
81 to 85	213
86 to 90	221
91 to 95	229
96 to 100	237

Table 2:

Number of Open-Response Question Points	Estimated MTEL Score
2	31
3	36
4	41
5	46
6	50
7	55
8	60

Use the form below to calculate your estimated practice test score.