ASVAB Mechanical Comprehension Practice Test 765814 Results

Your Results Global Average
Questions 5 5
Correct 0 2.99
Score 0% 60%

Review

1

Which of the following is the formula for gravitational potential energy?

61% Answer Correctly

\(PE = mg^2h\)

\(PE = { 1 \over 2} mv^2\)

\(PE = { 1 \over 2} mg^2\)

\(PE = mgh\)
Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s2).

2

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

65% Answer Correctly

energy

torque

rotational direction

force
Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

3

Normal force is generally equal to the __________ of an object.

61% Answer Correctly

coefficient of friction

density

weight

mass
Solution

Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.

4

Which class of lever offers no mechanical advantage?

45% Answer Correctly

first

third

second

none of these, all levers offer mechanical advantage
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.

5 A = 8 ft., the green box weighs 10 lbs., and the blue box weighs 20 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
1.33 ft.
160 ft.
0 ft.
4 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:

10 lbs. x 8 ft. = 20 lbs. x dB

dB = \( \frac{10 \times 8 ft⋅lb}{20 lbs.} \) = \( \frac{80 ft⋅lb}{20 lbs.} \) = 4 ft.