ASVAB Mechanical Comprehension Practice Test 689642 Results

Your Results Global Average
Questions 5 5
Correct 0 3.02
Score 0% 60%

Review

1 What is the efficiency of a machine has work input of 110 ft⋅lb and work output of 49 ft⋅lb?
67% Answer Correctly
180%
55%
90%
45%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{49 ft⋅lb}{110 ft⋅lb} \times 100 \) \( = 45% \) %
2

The standard unit of energy is the:

73% Answer Correctly

Horsepower

Watt

Volt

Joule
Solution

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

3 A 340 lb. barrel is rolled up a 6 ft. ramp to a platform that's 1 ft. tall. What effort is required to move the barrel?
53% Answer Correctly
56.7 lbs.
51 lbs.
51.7 lbs.
18.9 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. = 340 lbs. x 1 ft.
Fe = \( \frac{340 ft⋅lb}{6 ft.} \) = 56.7 lbs.

4

Boyle's law defines the relationship between pressure and volume as:

58% Answer Correctly

\(\frac{P_1}{P_2} = {V_1}{V_2}\)

\(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

\(\frac{P_1}{P_2} = \frac{V_1}{V_2}\)

\({P_1}{P_2} = {V_1}{V_2}\)
Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional". Expressed as a formula, that's \(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

5 A mass of air has a pressure of 6.0 psi and a volume of 30 ft.3. If the air is compressed to a new volume of 15 ft.3, what is the new pressure?
56% Answer Correctly
13.2 psi
14 psi
12 psi
6 psi
Solution

According to Boyle's Law, pressure and volume are inversely proportional:

\( \frac{P_1}{P_2} \) = \( \frac{V_2}{V_1} \)

In this problem, V2 = 15 ft.3, V1 = 30 ft.3 and P1 = 6.0 psi. Solving for P2:

P2 = \( \frac{P_1}{\frac{V_2}{V_1}} \) = \( \frac{6.0 psi}{\frac{15 ft.^3}{30 ft.^3}} \) = 12 psi