ASVAB Mechanical Comprehension Practice Test 147488 Results

Your Results Global Average
Questions 5 5
Correct 0 3.38
Score 0% 68%

Review

1 If you lift a 6 lbs. rock 8 ft. from the ground, how much work have you done?
71% Answer Correctly
96 ft⋅lb
14 ft⋅lb
48 ft⋅lb
None of these is correct
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 6 \times 8 \)
\( W = 48 \)
2 If the green box weighs 25 lbs. and 5 lbs. of force is applied 9 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?
55% Answer Correctly
5.4 ft.
0 ft.
1.8 ft.
0.9 ft.
Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{5 lbs. \times 9 ft.}{25 lbs.} \) = \( \frac{45 ft⋅lb}{25 lbs.} \) = 1.8 ft.

3

Hydraulics is the transmission of force through the use of which of the following?

73% Answer Correctly

gear systems

liquids

air pressure

torque
Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).

4 If 75 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow and the green box is 1 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
62% Answer Correctly
15 lbs.
375 lbs.
125 lbs.
1125 lbs.
Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{75 lbs. \times 5 ft.}{1 ft.} \) = \( \frac{375 ft⋅lb}{1 ft.} \) = 375 lbs.

5

Tension is a force that does which of the following?

75% Answer Correctly

slows an object

stretches an object

heats up an object

compacts an object
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.