ASVAB Mechanical Comprehension Practice Test 60741 Results

Your Results Global Average
Questions 5 5
Correct 0 2.79
Score 0% 56%

Review

1 If the radius of the axle is 3 and the radius of the wheel is 4, what is the mechanical advantage of this wheel and axle configuration?
52% Answer Correctly
3
4
-1
1.33
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 4 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{4}{3} \) = 1.33

2 If the green box weighs 15 lbs. and is 3 ft. from the fulcrum, how much weight would need to be placed at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 6 ft.?
63% Answer Correctly
90 lbs.
7.5 lbs.
1.88 lbs.
2 lbs.
Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{15 lbs. \times 3 ft.}{6 ft.} \) = \( \frac{45 ft⋅lb}{6 ft.} \) = 7.5 lbs.

3 If the radius of the axle is 3 and the radius of the wheel is 4, what is the mechanical advantage of this wheel and axle configuration?
41% Answer Correctly
1.33
1
0.75
4
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 4 for a mechanical advantage of \( \frac{3}{4} \) = 0.75

4

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

63% Answer Correctly

volume, mass

density, volume

pressure, volume

pressure, density
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".

5 The green box weighs 35 lbs. and a 55 lbs. weight is placed 5 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?
57% Answer Correctly
175 ft.
2.62 ft.
0 ft.
7.86 ft.
Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for da, our missing value, and plugging in our variables yields:

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{55 lbs. \times 5 ft.}{35 lbs.} \) = \( \frac{275 ft⋅lb}{35 lbs.} \) = 7.86 ft.