ASVAB Mechanical Comprehension Practice Test 450860 Results

Your Results Global Average
Questions 5 5
Correct 0 2.76
Score 0% 55%

Review

1

A wedge converts force applied to its blunt end into force __________ its inclined surface.

57% Answer Correctly

parallel to

along

perpendicular to

opposite to
Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

2 A = 5 ft., the green box weighs 15 lbs., and the blue box weighs 45 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
0.56 ft.
6.67 ft.
0.83 ft.
1.67 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:

15 lbs. x 5 ft. = 45 lbs. x dB

dB = \( \frac{15 \times 5 ft⋅lb}{45 lbs.} \) = \( \frac{75 ft⋅lb}{45 lbs.} \) = 1.67 ft.

3 If the handles of a wheelbarrow are 2.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 160 lbs. load concentrated at a point 1.5 ft. from the axle?
52% Answer Correctly
96
None of these is correct
42.7
240
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: Fede = Frdr. In this problem we're looking for effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{160 \times 1.5}{2.5} \)
\( F_e = \frac{240.0}{2.5} \)
\( F_e = 96 \)
4 If A = 12 ft., B = 2 ft., C = 8 ft., the green box weighs 35 lbs. and the blue box weighs 45 lbs., what does the orange box have to weigh for this lever to balance?
44% Answer Correctly
123.75 lbs.
41.25 lbs.
13.75 lbs.
165 lbs.
Solution
In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB + fCdC

For this problem, this equation becomes:

35 lbs. x 12 ft. = 45 lbs. x 2 ft. + fC x 8 ft.

420 ft. lbs. = 90 ft. lbs. + fC x 8 ft.

fC = \( \frac{420 ft. lbs. - 90 ft. lbs.}{8 ft.} \) = \( \frac{330 ft. lbs.}{8 ft.} \) = 41.25 lbs.

5

A shovel is an example of which class of lever?

56% Answer Correctly

a shovel is not a lever

second

third

first
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.