ASVAB Mechanical Comprehension Practice Test 82917 Results

Your Results Global Average
Questions 5 5
Correct 0 3.29
Score 0% 66%

Review

1 What is the power output of a 9 hp engine that's 30% efficient?
39% Answer Correctly
371.3 \( \frac{ft⋅lb}{s} \)
742.5 \( \frac{ft⋅lb}{s} \)
5940 \( \frac{ft⋅lb}{s} \)
1485 \( \frac{ft⋅lb}{s} \)
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 9 hp x 550 \( \frac{ft⋅lb}{s} \) = 4950 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{30 \times 4950 \frac{ft⋅lb}{s}}{100} \) \( = \frac{148500 \frac{ft⋅lb}{s}}{100} \) = 1485 \( \frac{ft⋅lb}{s} \)
2 What is the mechanical advantage of this inclined plane if the length of the ramp is 3 ft. and the height of the green box is 1 ft.?
82% Answer Correctly
4.5
3
3.3
7
Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:

MA = \( \frac{d_e}{d_r} \) = \( \frac{3 ft.}{1 ft.} \) = 3

3 If input effort is 500 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 7?
79% Answer Correctly
3500 ft⋅lb
875ft⋅lb
14000ft⋅lb
0ft⋅lb
Solution
Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 7 will multiply an input effort of 500 ft⋅lb by 7 to produce an output effort of 3500 ft⋅lb.
4

Which of the following surfaces would have the lowest coefficient of friction?

85% Answer Correctly

concrete

ice

leather

tile
Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other.  Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

5 If the radius of the axle is 3 and the radius of the wheel is 6, what is the mechanical advantage of this wheel and axle configuration?
41% Answer Correctly
0.5
2.0
3
6
Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 3 and the output radius (where the resistance is being applied) is 6 for a mechanical advantage of \( \frac{3}{6} \) = 0.5