ASVAB Mechanical Comprehension Practice Test 142338 Results

Your Results Global Average
Questions 5 5
Correct 0 2.95
Score 0% 59%

Review

1

The force amplification achieved by using a tool, mechanical device or machine system is called:

80% Answer Correctly

work

efficiency

power

mechanical advantage


Solution

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Such a device utilizes input force and trades off forces against movement to amplify and/or change its direction.


2

Which of the following is not true of a  first-class lever?

51% Answer Correctly

changes the direction of force

increases distance

decreases distance

increases force


Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.


3 A 430 lb. barrel is rolled up a 6 ft. ramp to a platform that's 5 ft. tall. What effort is required to move the barrel?
53% Answer Correctly
322.5 lbs.
358.3 lbs.
360.3 lbs.
361.3 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 6 ft. = 430 lbs. x 5 ft.
Fe = \( \frac{2150 ft⋅lb}{6 ft.} \) = 358.3 lbs.


4

Which of the following will increase the mechanical advantage of this inclined plane?

58% Answer Correctly

lower the force acting at the blue arrow

shorten the ramp

increase the force acting at the blue arrow

lengthen the ramp


Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In order to increase mechanical advantage, this ratio must increase which means making the effort distance longer and this can be accomplished by lengthening the length of the ramp.


5 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 180 lbs. load concentrated at a point 1.5 ft. from the axle?
52% Answer Correctly
108
59
270
300

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:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{180 \times 1.5}{2.5} \)
\( F_e = \frac{270.0}{2.5} \)
\( F_e = 108 \)