ASVAB Mechanical Comprehension Practice Test 260423 Results

Your Results Global Average
Questions 5 5
Correct 0 3.21
Score 0% 64%

Review

1 A = 4 ft., the green box weighs 30 lbs., and the blue box weighs 65 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
0.62 ft.
0.46 ft.
1.85 ft.
0.92 ft.
Solution
In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB

For this problem, the equation becomes:

30 lbs. x 4 ft. = 65 lbs. x dB

dB = \( \frac{30 \times 4 ft⋅lb}{65 lbs.} \) = \( \frac{120 ft⋅lb}{65 lbs.} \) = 1.85 ft.

2

Which of the following is the formula for torque?

62% Answer Correctly

τ = rF

τ = r/F

τ = F/r2

τ = F/r
Solution

Torque measures force applied during rotation: τ = rF.  Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).

3

Torque involves a perpendicular force applied to a lever arm that moves around a center of rotation. Increasing the length of the lever arm will do which of the following?

55% Answer Correctly

increase applied force

decrease applied force

increase torque

decrease torque
Solution

Torque measures force applied during rotation: τ = rF.  Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).

4 If you lift a 48 lbs. rock 21 ft. from the ground, how much work have you done?
71% Answer Correctly
69 ft⋅lb
27 ft⋅lb
1008 ft⋅lb
0 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 48 \times 21 \)
\( W = 1008 \)
5

A fixed pulley has a mechanical advantage of:

68% Answer Correctly

-1

2

0

1
Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.