ASVAB Mechanical Comprehension Practice Test 808954 Results

Your Results Global Average
Questions 5 5
Correct 0 2.89
Score 0% 58%

Review

1 What is the efficiency of a machine has work input of 120 ft⋅lb and work output of 108 ft⋅lb?
67% Answer Correctly
0%
90%
360%
1%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{108 ft⋅lb}{120 ft⋅lb} \times 100 \) \( = 90% \) %
2 What is the power output of a 1 hp engine that's 50% efficient?
40% Answer Correctly
50 \( \frac{ft⋅lb}{s} \)
68.8 \( \frac{ft⋅lb}{s} \)
275 \( \frac{ft⋅lb}{s} \)
0 \( \frac{ft⋅lb}{s} \)
Solution
\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), Pi becomes 1 hp x 550 \( \frac{ft⋅lb}{s} \) = 550 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{50 \times 550 \frac{ft⋅lb}{s}}{100} \) \( = \frac{27500 \frac{ft⋅lb}{s}}{100} \) = 275 \( \frac{ft⋅lb}{s} \)
3

What type of load creates different stresses at different locations on a structure?

60% Answer Correctly

impact load

static uniformly distributed load

non-uniformly distributed load

dynamic load
Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

4 A = 6 ft., the green box weighs 5 lbs., and the blue box weighs 15 lbs. What does distance B need to be for this lever to balance?
64% Answer Correctly
2 ft.
6 ft.
8 ft.
90 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:

5 lbs. x 6 ft. = 15 lbs. x dB

dB = \( \frac{5 \times 6 ft⋅lb}{15 lbs.} \) = \( \frac{30 ft⋅lb}{15 lbs.} \) = 2 ft.

5

Which of the following is the formula for hydraulic pressure?

58% Answer Correctly

P = F/A2

P = FA2

P = FA

P = F/A
Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).