ASVAB Mechanical Comprehension Practice Test 905243 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.73
Score	0%	55%

Review

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

45% Answer Correctly

	kinetic energy
	potential energy
	acceleration
	total mechanical energy

Solution

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

2 What's the mechanical advantage of a wedge that's 3 inches wide and 9 inches long?

83% Answer Correctly

	6
	9
	2.7
	3

Solution

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{9 in.}{3 in.} \) = 3

The advantage of using a third-class lever is that it increases:

37% Answer Correctly

	the speed of the load
	the mechanical advantage of the lever
	the force applied to the load
	the distance traveled by the load

Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

4 If the handles of a wheelbarrow are 2.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 120 lbs. load concentrated at a point 1.0 ft. from the axle?

52% Answer Correctly

	240
	60
	None of these is correct
	-16

Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. In this problem we're looking for effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{120 \times 1.0}{2.0} \)
\( F_e = \frac{120.0}{2.0} \)
\( F_e = 60 \)

An inclined plane increases ___________ to reduce ____________.

58% Answer Correctly

	force, power
	force, distance
	distance, force
	distance, power

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.