ASVAB Mechanical Comprehension Practice Test 505519 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.32
Score	0%	66%

Review

1 The radius of the axle is 7, the radius of the wheel is 12, and the blue box weighs 85 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	12 lbs.
	19 lbs.
	11.97 lbs.
	49.71 lbs.

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 12 and the output radius (where the resistance is being applied) is 7 for a mechanical advantage of \( \frac{12}{7} \) = 1.71

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{85 lbs.}{1.71} \) = 49.71 lbs.

The mass of an object correlates to the size of the object but ultimately depends on:

67% Answer Correctly

	the object's density
	the object's weight
	the object's potential energy
	gravity

Solution

Mass is a measure of the amount of matter in an object. In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

Which of the following surfaces would have the lowest coefficient of friction?

86% Answer Correctly

	ice
	leather
	tile
	concrete

Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

4 If the green box weighs 20 lbs. and is 5 ft. from the fulcrum, how much weight would need to be placed at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 6 ft.?

63% Answer Correctly

	50 lbs.
	16.67 lbs.
	120 lbs.
	8.33 lbs.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for R_b, our missing value, and plugging in our variables yields:

R_b = \( \frac{R_ad_a}{d_b} \) = \( \frac{20 lbs. \times 5 ft.}{6 ft.} \) = \( \frac{100 ft⋅lb}{6 ft.} \) = 16.67 lbs.

What is work?

61% Answer Correctly

	The potential for exertion
	Force per unit time
	Force per unit distance
	The movement of an object by a force

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.