ASVAB Mechanical Comprehension Practice Test 636819 Results

Your Results Global Average
Questions 5 5
Correct 0 2.76
Score 0% 55%

Review

1 10 lbs. of effort is used by a machine to lift a 20 lbs. box. What is the mechanical advantage of the machine?
84% Answer Correctly
2
5
1.8
-5
Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{20 lbs.}{10 lbs.} \) = 2

2

For a hydraulic system, pressure applied to the input of the system will increase the pressure in which parts of the system?

58% Answer Correctly

all of these are correct

the portions of the system at an altitude below the input

the portions of the system at an altitude above the input

everywhere in the system
Solution

Pascal's law states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. For a hydraulic system, this means that a pressure applied to the input of the system will increase the pressure everywhere in the system.

3 If the radius of the axle is 5 and the radius of the wheel is 10, what is the mechanical advantage of this wheel and axle configuration?
36% Answer Correctly
2
1
-5
0
Solution

The mechanical advantage of a wheel and axle lies in the difference in radius between the inner (axle) wheel and the outer wheel. But, this mechanical advantage is only realized when the input effort and load are applied to different wheels. Applying both input effort and load to the same wheel results in a mechanical advantage of 1.

4 The green box weighs 15 lbs. and a 70 lbs. weight is placed 3 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
0 ft.
5 ft.
14 ft.
3.5 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 = \( \frac{R_bd_b}{R_a} \) = \( \frac{70 lbs. \times 3 ft.}{15 lbs.} \) = \( \frac{210 ft⋅lb}{15 lbs.} \) = 14 ft.

5 If the radius of the axle is 5 and the radius of the wheel is 10, what is the mechanical advantage of this wheel and axle configuration?
41% Answer Correctly
10
2.0
0.5
-5
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 5 and the output radius (where the resistance is being applied) is 10 for a mechanical advantage of \( \frac{5}{10} \) = 0.5