ASVAB Mechanical Comprehension Practice Test 434702 Results

Your Results Global Average
Questions 5 5
Correct 0 3.49
Score 0% 70%

Review

1 If you lift a 21 lbs. rock 23 ft. from the ground, how much work have you done?
70% Answer Correctly
483 ft⋅lb
-2 ft⋅lb
1 ft⋅lb
230 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 21 \times 23 \)
\( W = 483 \)
2 If the handles of a wheelbarrow are 1.5 ft. from the wheel axle and the load is concentrated at a point 0.5 ft. from the axle, how many pounds of load will a 250 lbs. force lift?
47% Answer Correctly
101.2
65
750
83.3
Solution
This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: Fede = Frdr. In this problem we're looking for resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{250 \times 1.5}{0.5} \)
\( F_r = \frac{375.0}{0.5} \)
\( F_r = 750 \)
3

An object's resistance to changes in direction is known as:

81% Answer Correctly

weight

inertia

kinetic energy

mass
Solution

The more mass a substance has the more force is required to move it or to change its direction. This resistance to changes in direction is known as inertia.

4

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

third-class lever

second-class lever

inclined plane

first-class lever
Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

5

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

73% Answer Correctly

gear systems

air pressure

torque

liquids
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).