ASVAB Mechanical Comprehension Practice Test 636621 Results

Your Results Global Average
Questions 5 5
Correct 0 3.02
Score 0% 60%

Review

1

The principle of moments defines equilibrium in terms of:

53% Answer Correctly

power

speed

energy

torque
Solution

According to the principle of moments, you can maintain equilibrium if the moments (forces) tending to clockwise rotation are equal to the moments tending to counterclockwise rotation. Another name for these moments of force is torque.

2 If the green box weighs 50 lbs. and is 1 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
10 lbs.
2.5 lbs.
30 lbs.
0 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 = \( \frac{R_ad_a}{d_b} \) = \( \frac{50 lbs. \times 1 ft.}{5 ft.} \) = \( \frac{50 ft⋅lb}{5 ft.} \) = 10 lbs.

3 If input effort is 900 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 7?
79% Answer Correctly
6300 ft⋅lb
3150ft⋅lb
1575ft⋅lb
25200ft⋅lb
Solution
Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 7 will multiply an input effort of 900 ft⋅lb by 7 to produce an output effort of 6300 ft⋅lb.
4

A shovel is an example of which class of lever?

56% Answer Correctly

a shovel is not a lever

first

second

third
Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

5 A mass of air has a pressure of 12.0 psi and a volume of 60 ft.3. If the air is compressed to a new volume of 35 ft.3, what is the new pressure?
56% Answer Correctly
19.6 psi
23.6 psi
20.6 psi
41.1 psi
Solution

According to Boyle's Law, pressure and volume are inversely proportional:

\( \frac{P_1}{P_2} \) = \( \frac{V_2}{V_1} \)

In this problem, V2 = 35 ft.3, V1 = 60 ft.3 and P1 = 12.0 psi. Solving for P2:

P2 = \( \frac{P_1}{\frac{V_2}{V_1}} \) = \( \frac{12.0 psi}{\frac{35 ft.^3}{60 ft.^3}} \) = 20.6 psi