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# Mechanical Comprehension Practice Problems for McGraw-Hill's ASVAB (page 2)

By — McGraw-Hill Professional
Updated on Jun 26, 2011

1. B. In a class 1 lever, the fulcrum is between the effort and the load. Of the choices, only the pair of scissors has the same arrangement of elements. The tweezers (choice A) and tongs (choice B) are examples of class 3 levers. The wheelbarrow (choice C) is a class 2 lever.
2. D.In a class 2 lever, the fulcrum is at one end, the effort is at the other end, and the load is between the fulcrum and the effort. Of the choices, only the wheelbarrow has this arrangement of elements. The seesaw (choice A) and the scissors (choice B) are class 1 levers. The human forearm (choice C) is a class 3 lever.
3. B.Air is a gas, so according to the gas laws, when a mass of warm air expands, it will most likely cool down.
4. A.In a class 3 lever, the fulcrum is at one end, the load is at the other, and the effort is between the fulcrum and the load. Of the choices, only the tweezers have this arrangement of elements. The wheelbarrow (choice B) is a class 2 lever. The seesaw (choice C) is a class 1 lever. The wedge (choice D) is not a lever at all but an inclined plane.
5. B.Metal is a better conductor of heat than wood or plastic, so the metal fork would feel hottest to the touch.
6. C.MA = load/effort. 300/60 = 5
7. A.MA = effort distance/load distance. 4 = 8/load distance. 4 = 8/2. The load distance is 2 ft.
8. B.The leak of 2 gal/sec = 120 gal/min. Net gain is 60 gal/min, so it will take 2 minutes to add 120 gallons to the tank.
9. D.Because water cannot be compressed, the same amount of water must be flowing through both parts of the pipe system. This makes choice C incorrect. If the same amount of water is flowing through all parts of the system, then the water must be flowing faster in the 1-inch section, reducing pressure in that section. That makes choices A and B both incorrect.
10. B.The ratio of teeth is 18 to 12. Each turn of gear A will turn gear B 1.5 times. 1.5 × 3 = 4.5.
11. A.Count the supporting strands (the strands of rope that will be shortened as the load is lifted). There are two supporting strands, so MA = 2.
12. D.Since the load is centered between the posts, each post carries equal weight.
13. C.When fluid speed increases, pressure decreases. Because the same amount of water must be in these pipes, water must be moving faster at point B. Therefore pressure is lower at point B.
14. A.The only way to distort the form of a triangular- shaped structure is to break the legs or angles. That makes triangles sturdier than other structural shapes, which is a good reason to use triangle shapes when constructing a bridge.