ASVAB Mechanical Comprehension Practice Test 226294 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.30
Score	0%	66%

Review

1 If A = 6 ft. and the green box weighs 10 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	60 ft⋅lb
	120 ft⋅lb
	1 ft⋅lb
	180 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 10 ft. x 6 lbs. = 60 ft⋅lb

2 If you have a gear train with two gears, the first with 32 teeth and the second with 8 teeth, how many revolutions does the second gear make for each revolution of the first gear?

77% Answer Correctly

	4
	2
	12
	1

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 = \( \frac{N_1}{N_2} \) = \( \frac{32}{8} \) = 4

3 If the handles of a wheelbarrow are 1.0 ft. from the wheel axle and the load is concentrated at a point 0.5 ft. from the axle, how many pounds of load will a 270 lbs. force lift?

47% Answer Correctly

	None of these is correct
	0
	540
	270

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:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{270 \times 1.0}{0.5} \)
\( F_r = \frac{270.0}{0.5} \)
\( F_r = 540 \)

4 If 15 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow and the green box is 1 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

62% Answer Correctly

	3 lbs.
	37.5 lbs.
	75 lbs.
	150 lbs.

Solution

To balance this lever the torques at the green box and the blue arrow 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 green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{15 lbs. \times 5 ft.}{1 ft.} \) = \( \frac{75 ft⋅lb}{1 ft.} \) = 75 lbs.

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

66% Answer Correctly

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