ASVAB Mechanical Comprehension Practice Test 166154 Results

Your Results Global Average
Questions 5 5
Correct 0 3.30
Score 0% 66%

Review

1 If the green box weighs 65 lbs. and is 3 ft. from the fulcrum, how much force would need to be applied at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 5 ft.?
62% Answer Correctly
0 lbs.
19.5 lbs.
39 lbs.
325 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 Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{65 lbs. \times 3 ft.}{5 ft.} \) = \( \frac{195 ft⋅lb}{5 ft.} \) = 39 lbs.

2

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

position of the fulcrum

output force 

output distance

input force
Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

3

A a seesaw / teeter-totter is an example of which of the following?

69% Answer Correctly

third-class lever

inclined plane

second-class lever

first-class lever
Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

4 The radius of the axle is 3, the radius of the wheel is 8, and the blue box weighs 70 lbs. What is the effort force necessary to balance the load?
53% Answer Correctly
26.22 lbs.
10.67 lbs.
21.36 lbs.
5.67 lbs.
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 3 for a mechanical advantage of \( \frac{8}{3} \) = 2.67

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{70 lbs.}{2.67} \) = 26.22 lbs.

5

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

80% Answer Correctly

work

heat

power

 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.