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LearningExpress Editors Updated on Aug 12, 2011
These mechanical comprehension practice questions are based on the actual ASVAB. Take this quiz to see how you would do if you took the exam today and to determine your strengths and weaknesses as you plan your study schedule.
Time: 19 minutes
- Two blocks of equal weight are suspended by a pulley. The blocks are 10 vertical feet apart. How far must block A be pulled down to be at equal height with block B?
- 5 feet
- 10 feet
- 15 feet
- 20 feet
- If gear 2 turns counterclockwise, which other gear(s), if any, will turn clockwise?
- 1 only
- 3 only
- 3 and 4 only
- 1, 3, and 4
- Lenny leaves camp at 6:00 A.M. and jogs north at 8 mph. George leaves camp half an hour later and follows the same path as Lenny at 10 mph. At what time will George catch Lenny?
- 7:00 A.M.
- 7:30 A.M.
- 8:00 A.M.
- 8:30 A.M.
- A 240-pound block is being pulled up an incline by a pulley. The incline rises 8 feet. Neglecting friction, if 60 pounds of force is necessary to move the block up the incline, how long is the incline?
- 60 feet
- 32 feet
- 16 feet
- 30 feet
- What is the mechanical advantage of the pulley system shown here?
- 1
- 2
- 3
- 4
- In the diagram, Cory wants to lift a block using a lever. The block is 8 feet from the pivot point and Cory is 12 feet from the pivot point. If it takes 200 pounds of force to lift the block, how much does it weigh?
- 96 pounds
- 400 pounds
- 300 pounds
- 200 pounds
- The same type of plastic is used to make blocks of 3 cubes of different sizes. The first has a weight of 0.5 pounds, the second has a weight of 0.75 pounds, and the third has a weight of 1.5 pounds. Which of the following statements is true?
- All three cubes will either float or sink.
- Cube 1 will float and cubes 2 and 3 will sink.
- Cube 3 will float and cubes 1 and 2 will sink.
- Cubes 1 and 2 will float and cube 3 will sink.
- A force of 8 pounds is required to move a spring 4 inches. How much force is required to move the spring 1 foot?
- 3 pounds
- 12 pounds
- 24 pounds
- 36 pounds
- A screw has 7 threads per inch. How many full turns are necessary for the nut to travel 3 inches?
- 12 turns
- 15 turns
- 18 turns
- 21 turns
- Why is oil added to an engine?
- Engines burn oil.
- Oil helps gasoline burn better.
- Oil increases friction in the engine.
- Oil decreases friction in the engine.
- Using the pulley system shown, how much force is required to lift an 80-pound weight?
- 20 pounds
- 40 pounds
- 80 pounds
- 160 pounds
- Raising a flag up a flagpole is most commonly accomplished with what simple machine?
- a lever
- a pulley
- an inclined plane
- a gear
- If gear 2 turns clockwise, which other gear(s), if any, will turn clockwise?
- 1 only
- 3 only
- 1 and 3
- none
- In the diagram, Andre wants to lift a 126-pound block using a lever. If the block is 12 feet from the pivot point and Andre is 12 feet beyond that, how much force must he apply to lift the block?
- 126 pounds
- 63 pounds
- 75 pounds
- 144 pounds
- The shock absorber on a car is a very large spring. If a car hits a pothole with 500 pounds of force and the shock absorber compresses 2.5 inches, what is its force constant?
- 200 pounds per inch
- 300 pounds per inch
- 350 pounds per inch
- 400 pounds per inch
- A cracked pipe, marked in the figure by an ×, has caused all valves to automatically close. Which valves can be opened to allow water to flow from tank A to tank B while avoiding the broken section?
- 1 and 3
- 1 and 4
- 1, 2, and 5
- 1, 3, and 5
- A single-speed bicycle has a front gear with 48 teeth and a rear gear with 12 teeth. If the bicycle is pedaled at 90 rpm, how fast will the rear wheel rotate?
- 90 rpm
- 180 rpm
- 270 rpm
- 360 rpm
- AA block is held in place on a ramp by friction. Which arrow shows the direction of the frictional force?
- A
- B
- C
- D
- If the following items are placed into a hot oven, which will warm most quickly?
- a metal fork
- a plastic spoon
- a ceramic m
- a glass bowl
- Using the pulley system shown in the figure, how much force is required to lift a 300-pound weight?
- 75 pounds
- 100 pounds
- 150 pounds
- 300 pounds
- A screw can be thought of as a special type of what simple machine?
- the lever
- the inclined plane
- the pulley
- the wheel and axle
- In the diagram, Steven wants to balance two blocks on either side of a lever. One block weighs 57 pounds and the other weighs 76 pounds. If the 57-pound block is 6 feet to the left of the pivot point, how far to the right of the pivot point should the 76-pound block be placed?
- 4.5 feet
- 6 feet
- 19 feet
- 4 feet
- Two ramps can be used to raise a heavy barrel up to a platform. Neglecting friction, which ramp requires less work to raise the barrel?
- Ramp A requires less work.
- Ramp B requires less work.
- They require the same amount of work.
- It is impossible to determine.
- Pulleys A and B are identical in size and connected by a belt. If pulley A rotates at 20 rpm clockwise, at what rate and in what direction will pulley B rotate?
- 20 rpm, clockwise
- 20 rpm, counterclockwise
- 40 rpm, clockwise
- 40 rpm, counterclockwise
- A 270-pound block is being pulled up an incline by a pulley. The incline is 36 feet long and rises 4 feet. Neglecting friction, how much force is necessary to move the block up the incline?
- 30 pounds
- 270 pounds
- 40 pounds
- 144 pounds
Answers
- a. Every foot block A is lowered will raise block B by the same amount. To equalize the 10-foot difference, block A must be lowered 10 feet ÷ 2 = 5 feet.
- d. Gear 2 turning counterclockwise will lead all gears it touches to turn clockwise.
- d. When George leaves, Lenny will have already traveled 8 mph × 0.5 hours = 4 miles. George runs 2 mph faster than Lenny. Since Lenny got a 4-mile head start, it will take George 4 miles ÷ 2 mph = 2 hours to catch Lenny. Since George left at 6:30 A.M., he will catch Lenny at 8:30 A.M.
- b. Mechanical advantage (MA) is the factor by which a simple machine multiplies for the force put into it. In this case, 60 pounds of force is used to move a 240-pound block, so MA = 240 ÷ 60 = 4. The MA of a ramp is determined by the length of the ramp, l, divided by the height gained, h. In this case, MA = 3 = = l8 feet. Solving for l tells us the ramp is 32 feet long.
- d. The weight of the load is spread over 4 cables, so the mechanical advantage is 4.
- c. w_{1} × d_{1} = w_{2} × d_{2}. w_{1} × 8 feet = 200 pounds × 12 feet. Solving for w_{1} gives 300 pounds.
- a. Each block will have a different size and weight, but, since each is made from the same material, they will all have the same density. Since an object's density determines whether it will float or sink in water, all three objects will either float or sink.
- c. If 8 pounds of force will move a spring 4 inches, it has a force constant of 8 pounds ÷ 4 inches = 2 pounds per inch. Moving the spring 12 inches will require 12 inches × 2 pounds per inch = 24 pounds of force.
- d. There are 7 threads per inch. To move the nut 3 inches will require 7 × 3 = 21 turns. d. Oil is a lubricant used to decrease the amount of friction between the many moving parts in an engine.
- c. The mechanical advantage of this pulley system is 2. The force required to lift the 80-pound load is 80 pounds ÷ 1 = 80 pounds.
- b. A single fixed pulley has the advantage of being able to change the direction of force. Thus, a flag can be raised up a flagpole without having to climb and lift it.
- d. Gear 2 turning clockwise will cause the neighboring gears to turn counterclockwise, so no other gears will turn clockwise.
- b. w_{1} × d_{1} = w_{2} × d_{2}. Andre is 24 feet away from the pivot point. 126 pounds × 12 feet = 12 feet × w_{2}. Solving for w_{2} gives 63 pounds.
- a. 500 pounds ÷ 2.5 inches = 200 pounds per inch.
- b. Valves 2, 3, and 5 are all directly connected to the break and so must remain closed. 1 and 4 may be opened to successfully route the flow from A to B.
- d. Each full turn of the pedals will turn the rear wheel 48 ÷ 12 = 4 revolutions. If the pedals are turning at 90 rpm, the rear wheel will move at 4 × 90 rpm = 360 rpm.
- d. Frictional forces point in the opposite direction of motion (arrow B).
- a. Of the materials listed, metal objects are the best at conducting heat and therefore will warm the fastest. Plastic, glass, and ceramic are all good insulators and thus will take a long time to absorb heat.
- c. A pulley system of this type has a mechanical advantage of 2. So, to lift a 300-pound weight will require 300 pounds ÷ 2 = 150 pounds.
- b. A screw is a special type of inclined plane where the ramp is wrapped around a cylindrical object.
- a. w_{1} × d_{1} = w_{2} × d_{2}. 57 pounds × 6 feet = 76 pounds × d_{2}. Solving for d_{2} gives 4.5 feet.
- c. While ramp B offers a greater mechanical advantage, the amount of work is determined by the overall change in height of the barrel. Since the barrel is raised the same height regardless of which ramp is used, the amount of work done is the same.
- a. Since A and B are identical in size, they will rotate at the same rate. The belt connects the two, so A and B also rotate in the same direction.
- a. The mechanical advantage (MA) of a ramp is determined by the length of the ramp, l, divided by the height gained, h. In this case, MA = = 36 feet ÷ 4 feet = 9. The force required to pull a 270-pound block up a ramp is 270 pounds ÷ 9 = 30 pounds.
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From ASVAB: Power Practice. Copyright © 2010 by LearningExpress, LLC. All Rights Reserved.