ASVAB Mechanical Comprehension Practice Test 116959 Results

Your Results Global Average
Questions 5 5
Correct 0 3.52
Score 0% 70%

Review

1 60 lbs. of effort is used by a machine to lift a 420 lbs. box. What is the mechanical advantage of the machine?
84% Answer Correctly
7.7
21
7
15
Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{420 lbs.}{60 lbs.} \) = 7

2 What is the efficiency of a machine has work input of 145 ft⋅lb and work output of 72 ft⋅lb?
68% Answer Correctly
12%
2%
50%
200%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{72 ft⋅lb}{145 ft⋅lb} \times 100 \) \( = 50% \) %
3

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

force or distance

power or distance

force or speed

speed or power
Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

4 What is the mechanical advantage of this inclined plane if the length of the ramp is 14 ft. and the height of the green box is 7 ft.?
82% Answer Correctly
2
6
5
4
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 = \( \frac{d_e}{d_r} \) = \( \frac{14 ft.}{7 ft.} \) = 2

5

The mechanical advantage of connected gears is proportional to which characteristic of the gears?

73% Answer Correctly

diameter

number of teeth

circumference

speed
Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear.  For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.