ASVAB Mechanical Comprehension Practice Test 436800 Results

Your Results Global Average
Questions 5 5
Correct 0 2.83
Score 0% 57%

Review

1 A = 7 ft., the green box weighs 35 lbs., and the blue box weighs 50 lbs. What does distance B need to be for this lever to balance?
64% Answer Correctly
2.45 ft.
9.8 ft.
350 ft.
4.9 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:

35 lbs. x 7 ft. = 50 lbs. x dB

dB = \( \frac{35 \times 7 ft⋅lb}{50 lbs.} \) = \( \frac{245 ft⋅lb}{50 lbs.} \) = 4.9 ft.

2

The mechanical advantage of a third class lever is always:

37% Answer Correctly

equal to one

less than 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.

3 A 280 lb. barrel is rolled up a 14 ft. ramp to a platform that's 2 ft. tall. What effort is required to move the barrel?
53% Answer Correctly
60 lbs.
13.3 lbs.
120 lbs.
40 lbs.
Solution

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

Fede = Frdr

Plugging in the variables from this problem yields:

Fe x 14 ft. = 280 lbs. x 2 ft.
Fe = \( \frac{560 ft⋅lb}{14 ft.} \) = 40 lbs.

4 What's the mechanical advantage of a wedge that's 5 inches wide and 15 inches long?
83% Answer Correctly
2.7
9
3
5
Solution

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{15 in.}{5 in.} \) = 3

5

Which of the following represents the force a surface exerts when an object presses against it?

48% Answer Correctly

friction

counter force

mass

normal force
Solution

Normal force (FN) represents the force a surface exerts when an object presses against it.