ASVAB Mechanical Comprehension Practice Test 270312 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.68
Score	0%	54%

Review

Which of these is the formula for force?

77% Answer Correctly

	F = m/a
	F = a/m
	F = ma
	F = am²

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.

2 If the handles of a wheelbarrow are 2.5 ft. from the wheel axle and the load is concentrated at a point 1.0 ft. from the axle, how many pounds of load will a 140 lbs. force lift?

47% Answer Correctly

	53.1
	350
	140
	None of these is correct

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 resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{140 \times 2.5}{1.0} \)
\( F_r = \frac{350.0}{1.0} \)
\( F_r = 350 \)

The measure of how much of the power put into a machine is turned into movement or force is called:

56% Answer Correctly

	power
	force multiplication
	mechanical advantage
	efficiency

Solution

The efficiency of a machine describes how much of the power put into the machine is turned into movement or force. A 100% efficient machine would turn all of the input power into output movement or force. However, no machine is 100% efficient due to friction, heat, wear and other imperfections that consume input power without delivering any output.

The mechanical advantage of a third class lever is always:

37% Answer Correctly

	less than one
	equal to one
	not equal to one
	greater than one

Solution

A third class lever is designed to multiply distance and speed at the expense of effort force. Because the effort force is greater than the resistance, the mechanical advantage of a third class lever is always less than one.

An example of a third class lever is a broom. The fulcrum is at your hand on the end of the broom, the effort force is your other hand in the middle, and the resistance is at the bottom bristles. The effort force of your hand in the middle multiplies the distance and speed of the bristles at the bottom but at the expense of producing a brushing force that's less than the force you're applying with your hand.

5 If the radius of the axle is 5 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?

41% Answer Correctly

	-3
	5
	8
	0.63

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 5 and the output radius (where the resistance is being applied) is 8 for a mechanical advantage of \( \frac{5}{8} \) = 0.63