ASVAB Mechanical Comprehension Practice Test 918962 Results

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

Review

1 A 390 lb. barrel is rolled up a 14 ft. ramp to a platform that's 4 ft. tall. What effort is required to move the barrel?
53% Answer Correctly
334.3 lbs.
100.3 lbs.
110.4 lbs.
111.4 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. = 390 lbs. x 4 ft.
Fe = \( \frac{1560 ft⋅lb}{14 ft.} \) = 111.4 lbs.

2

Power is the rate at which:

63% Answer Correctly

potential energy is converted into kinetic energy

work is done

input force is transferred to output force

friction is overcome
Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

3

The advantage of using a third-class lever is that it increases:

37% Answer Correctly

the force applied to the load

the speed of the load

the mechanical advantage of the lever

the distance traveled by the load
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.

4 What is the efficiency of a machine has work input of 235 ft⋅lb and work output of 82 ft⋅lb?
68% Answer Correctly
35%
8%
0%
2%
Solution
Due to friction, a machine will never be able to utilize 100% of its work input. A certain percentage of that input will be lost in overcoming friction within the machine. Effeciency is a measure of how much of a machine's work input can be turned into useful work output and is calculated by dividing work output by work input and multiplying the result by 100:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{82 ft⋅lb}{235 ft⋅lb} \times 100 \) \( = 35% \) %
5

A shovel is an example of which class of lever?

56% Answer Correctly

a shovel is not a lever

first

second

third
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.