ASVAB Mechanical Comprehension Practice Test 502896 Results

Your Results Global Average
Questions 5 5
Correct 0 3.34
Score 0% 67%

Review

1 What is the efficiency of a machine has work input of 235 ft⋅lb and work output of 129 ft⋅lb?
67% Answer Correctly
45%
110%
55%
27%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{129 ft⋅lb}{235 ft⋅lb} \times 100 \) \( = 55% \) %
2

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

1

0

4

2
Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement.  So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

3

The standard unit of energy is the:

73% Answer Correctly

Horsepower

Watt

Joule

Volt
Solution

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).

4 A 370 lb. barrel is rolled up a 17 ft. ramp to a platform that's 2 ft. tall. What effort is required to move the barrel?
53% Answer Correctly
43.5 lbs.
14.5 lbs.
45 lbs.
21.8 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 17 ft. = 370 lbs. x 2 ft.
Fe = \( \frac{740 ft⋅lb}{17 ft.} \) = 43.5 lbs.

5

Power is the rate at which:

62% Answer Correctly

input force is transferred to output force

friction is overcome

work is done

potential energy is converted into kinetic energy
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.