ASVAB Mechanical Comprehension Practice Test 525128 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.63
Score	0%	73%

Review

An object's resistance to changes in direction is known as:

82% Answer Correctly

	inertia
	weight
	kinetic energy
	mass

Solution

The more mass a substance has the more force is required to move it or to change its direction. This resistance to changes in direction is known as inertia.

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

	0
	1
	4
	2

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

3 If the green box is 7 ft. from the fulcrum and a certain force applied 2 ft. from the fulcrum at the blue arrow balances the lever, what is the mechanical advantage?

61% Answer Correctly

	0.57
	0.43
	0.29
	0.86

Solution

Because this lever is in equilibrium, we know that the effort force at the blue arrow is equal to the resistance weight of the green box. For a lever that's in equilibrium, one method of calculating mechanical advantage (MA) is to divide the length of the effort arm (E_a) by the length of the resistance arm (R_a):

MA = \( \frac{E_a}{R_a} \) = \( \frac{2 ft.}{7 ft.} \) = 0.29

When a lever is in equilibrium, the torque from the effort and the resistance are equal. The equation for equilibrium is R_ad_a = R_bd_b where a and b are the two points at which effort/resistance is being applied to the lever.

In this problem, R_a and R_b are such that the lever is in equilibrium meaning that some multiple of the weight of the green box is being applied at the blue arrow. For a lever, this multiple is a function of the ratio of the distances of the box and the arrow from the fulcrum. That's why, for a lever in equilibrium, only the distances from the fulcrum are necessary to calculate mechanical advantage.

If the lever were not in equilibrium, you would first have to calculate the forces and distances necessary to put it in equilibrium and then divide E_a by R_a to get the mechanical advantage.

Which of the following is not a type of simple machine?

58% Answer Correctly

	gear
	lever
	pulley
	screw

Solution

The six types of simple machines are the lever, wheel and axle, pulley, inclined plane, wedge, and screw.

5 If input effort is 900 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 7?

79% Answer Correctly

	1575ft⋅lb
	0ft⋅lb
	3150ft⋅lb
	6300 ft⋅lb

Solution

Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 7 will multiply an input effort of 900 ft⋅lb by 7 to produce an output effort of 6300 ft⋅lb.