ASVAB Mechanical Comprehension Practice Test 532517 Results

Your Results Global Average
Questions 5 5
Correct 0 3.41
Score 0% 68%

Review

1 20 lbs. of effort is used by a machine to lift a 140 lbs. box. What is the mechanical advantage of the machine?
84% Answer Correctly
21
14
7
7.7
Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{140 lbs.}{20 lbs.} \) = 7

2

What is work?

60% Answer Correctly

Force per unit time

The movement of an object by a force

The potential for exertion

Force per unit distance
Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.

3 If this lever is in equilibrium with an effort force of 7.5 ft. lb. at the blue arrow and a resistance force of 6 ft. lb. at the green box, what is its mechanical advantage?
48% Answer Correctly
0.8
0.88
2.8
0.4
Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{6 ft.}{7.5 ft.} \) = 0.8

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.8 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.

4 How much resistance could a 90 lb. effort force lift using a block and tackle pulley that has 10 ropes supporting the resistance?
81% Answer Correctly
1800 lbs.
902 lbs.
900 lbs.
990 lbs.
Solution

The mechanical advantage (MA) of a block and tackle pulley is equal to the number of times the effort force changes direction. An easy way to count how many times the effort force changes direction is to count the number of ropes that support the resistance which, in this problem, is 10. With a MA of 10, a 90 lbs. effort force could lift 90 lbs. x 10 = 900 lbs. resistance.

5

A a seesaw / teeter-totter is an example of which of the following?

69% Answer Correctly

third-class lever

first-class lever

inclined plane

second-class lever
Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.