ASVAB Mechanical Comprehension Practice Test 375683 Results

Your Results Global Average
Questions 5 5
Correct 0 3.25
Score 0% 65%

Review

1 If you lift a 14 lbs. rock 23 ft. from the ground, how much work have you done?
71% Answer Correctly
644 ft⋅lb
1 ft⋅lb
322 ft⋅lb
161 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 14 \times 23 \)
\( W = 322 \)
2

Potential energy is energy that has the potential to be converted into what?

80% Answer Correctly

heat

power

work

 kinetic energy
Solution

Potential energy is the energy of an object by virtue of its position relative to other objects. It is energy that has the potential to be converted into kinetic energy.

3 If the green box weighs 15 lbs. and is 7 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 2 ft.?
63% Answer Correctly
157.5 lbs.
52.5 lbs.
13.13 lbs.
26.25 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 = \( \frac{R_ad_a}{d_b} \) = \( \frac{15 lbs. \times 7 ft.}{2 ft.} \) = \( \frac{105 ft⋅lb}{2 ft.} \) = 52.5 lbs.

4 If a 5 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow and the green box is 8 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
0.94 lbs.
1.88 lbs.
7.5 lbs.
3.75 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 Ra, our missing value, and plugging in our variables yields:

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{5 lbs. \times 3 ft.}{8 ft.} \) = \( \frac{15 ft⋅lb}{8 ft.} \) = 1.88 lbs.

5

A truck is using a rope to pull a car. Tension in the rope is greatest in which of the following places?

50% Answer Correctly

near the truck

in the middle

near the car

tension is equal in all parts of the rope
Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.