ASVAB Mechanical Comprehension Practice Test 252572 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.26
Score	0%	65%

Review

1 If you lift a 43 lbs. rock 44 ft. from the ground, how much work have you done?

71% Answer Correctly

	87 ft⋅lb
	1892 ft⋅lb
	None of these is correct
	924 ft⋅lb

Solution

Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 43 \times 44 \)
\( W = 1892 \)

2 If you have a gear train with three gears, the first with 22 teeth, the second with 14 teeth, and the third with 8 teeth, what is its mechanical advantage?

50% Answer Correctly

	2.8
	2.5
	-5.3
	5.5

Solution

The mechanical advantage of a gear train is its gear ratio. The gear ratio (V_r) is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have three gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{22}{14} \) \( \frac{14}{8} \) = \( \frac{22}{8} \) = 2.8

When it comes to force, mass and acceleration have what kind of relationship?

66% Answer Correctly

	inverse
	logarithmic
	linear
	exponential

Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.

Which of the following will increase the mechanical advantage of a second-class lever?

55% Answer Correctly

	move the object being lifted closer to the fulcrum
	move the object being lifted farther away from the fulcrum
	decrease the length of the lever
	move the fulcrum between the force and the object being lifted

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.

A ramp is an example of which kind of simple machine?

84% Answer Correctly

	wedge
	first-class lever
	inclined plane
	none of these

Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.