ASVAB Mechanical Comprehension Practice Test 737802 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.78
Score	0%	76%

Review

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

79% Answer Correctly

	4
	0
	1
	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.

2 If the green box is 8 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

	0.23
	0.25
	6.25
	0.28

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 = \( \frac{E_a}{R_a} \) = \( \frac{2 ft.}{8 ft.} \) = 0.25

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.

3 70 lbs. of effort is used by a machine to lift a 420 lbs. box. What is the mechanical advantage of the machine?

84% Answer Correctly

	6
	-1
	9
	10

Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{420 lbs.}{70 lbs.} \) = 6

Potential energy is energy that has the potential to be converted into what?

80% Answer Correctly

	power
	kinetic energy
	heat
	work

Solution

Potential energy is the energy of an object by virtue of its position relative to other objects. It is energy that has the potential to be converted into kinetic energy.

Hydraulics is the transmission of force through the use of which of the following?

73% Answer Correctly

	torque
	gear systems
	air pressure
	liquids

Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).