ASVAB Mechanical Comprehension Practice Test 28064 Results

Your Results Global Average
Questions 5 5
Correct 0 3.05
Score 0% 61%

Review

1

Which of the following is the formula for gravitational potential energy?

61% Answer Correctly

\(PE = { 1 \over 2} mv^2\)

\(PE = { 1 \over 2} mg^2\)

\(PE = mgh\)

\(PE = mg^2h\)
Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s2).

2 A = 5 ft., the green box weighs 35 lbs., and the blue box weighs 80 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
0.55 ft.
175 ft.
2.19 ft.
7 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:

35 lbs. x 5 ft. = 80 lbs. x dB

dB = \( \frac{35 \times 5 ft⋅lb}{80 lbs.} \) = \( \frac{175 ft⋅lb}{80 lbs.} \) = 2.19 ft.

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
5
-5
1
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

On Earth, acceleration due to gravity (g) is approximately __________. 

81% Answer Correctly

1 m/s2

6.67 x 10-11 m/s2

9.8 m/s2

1 m/s
Solution

Newton's Law of Univeral Gravitation defines the general formula for the attraction of gravity between two objects:  \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) . In the specific case of an object falling toward Earth, the acceleration due to gravity (g) is approximately 9.8 m/s2. 

5 If the radius of the axle is 7 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?
52% Answer Correctly
7
1
1.14
0.88
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 8 and the output radius (where the resistance is being applied) is 7 for a mechanical advantage of \( \frac{8}{7} \) = 1.14