ASVAB Mechanical Comprehension Practice Test 922400 Results

Your Results Global Average
Questions 5 5
Correct 0 3.03
Score 0% 61%

Review

1

A shovel is an example of which class of lever?

56% Answer Correctly

first

second

a shovel is not a lever

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.

2

Which of the following represents how much two materials resist sliding across each other?

53% Answer Correctly

coefficient of friction

normal friction

static friction

kinetic friction
Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other.  Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

3 If A = 7 ft. and the green box weighs 10 lbs. what is the torque acting on the A side of this lever?
75% Answer Correctly
0 ft⋅lb
17 ft⋅lb
280 ft⋅lb
70 ft⋅lb
Solution
For a lever, torque is weight x distance from the fulcrum which, in this case, is: 10 ft. x 7 lbs. = 70 ft⋅lb
4 If the green box weighs 20 lbs. and is 9 ft. from the fulcrum, how much weight would need to be placed at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 8 ft.?
63% Answer Correctly
22.5 lbs.
0 lbs.
67.5 lbs.
7.5 lbs.
Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

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

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{20 lbs. \times 9 ft.}{8 ft.} \) = \( \frac{180 ft⋅lb}{8 ft.} \) = 22.5 lbs.

5 If the green box weighs 25 lbs. and 70 lbs. of force is applied 5 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
4.67 ft.
0 ft.
14 ft.
56 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 = \( \frac{R_bd_b}{R_a} \) = \( \frac{70 lbs. \times 5 ft.}{25 lbs.} \) = \( \frac{350 ft⋅lb}{25 lbs.} \) = 14 ft.