ASVAB Mechanical Comprehension Practice Test 381590 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.01
Score	0%	60%

Review

Lisa lifts a 25 pound box from the floor onto a loading dock 4 ft. off the ground. Sam slides the same box along a ramp to move it up another 4 ft. onto a flatbed truck. Who has done more work?

50% Answer Correctly

	Sam
	They have done an equal amount of work
	Neither have done any work
	Lisa

Solution

Work is force multiplied by distance. Because both Connie and Sam moved the same weight the same distance they have done an equal amount of work. Sam employed the mechnacial advantage of an inclined plane so he exerted less effort to do the work but the amount of work done was still the same.

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

66% Answer Correctly

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

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 is not true of a first-class lever?

51% Answer Correctly

	decreases distance
	changes the direction of force
	increases force
	increases distance

Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

4 If you have a gear train with two gears, the first with 36 teeth and the second with 16 teeth, how many revolutions does the second gear make for each revolution of the first gear?

77% Answer Correctly

	2.3
	1.1
	6.8
	2.5

Solution

The gear ratio (V_r) of a gear train 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 only two gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) = \( \frac{36}{16} \) = 2.3

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

	its mass
	its speed
	its direction
	its weight

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.