ASVAB Mechanical Comprehension Practice Test 777565 Results

Your Results Global Average
Questions 5 5
Correct 0 2.77
Score 0% 55%

Review

1 If the handles of a wheelbarrow are 1.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 110 lbs. load concentrated at a point 0.5 ft. from the axle?
52% Answer Correctly
281.5
110
-82
55
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 effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{110 \times 0.5}{1.0} \)
\( F_e = \frac{55.0}{1.0} \)
\( F_e = 55 \)
2

A fixed pulley has a mechanical advantage of:

68% Answer Correctly

0

2

1

-1
Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

3

Torque involves a perpendicular force applied to a lever arm that moves around a center of rotation. Increasing the length of the lever arm will do which of the following?

55% Answer Correctly

decrease torque

increase torque

decrease applied force

increase applied force
Solution

Torque measures force applied during rotation: τ = rF.  Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).

4

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

its weight

its mass

its speed

its direction
Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

5 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 170 lbs. force lift?
47% Answer Correctly
255
31.3
0
510
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:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{170 \times 1.5}{0.5} \)
\( F_r = \frac{255.0}{0.5} \)
\( F_r = 510 \)