ASVAB Mechanical Comprehension Practice Test 286950 Results

Your Results Global Average
Questions 5 5
Correct 0 3.29
Score 0% 66%

Review

1

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

80% Answer Correctly

heat

power

work

 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.


2 If you have a gear train with three gears, the first with 28 teeth, the second with 14 teeth, and the third with 2 teeth, what is its mechanical advantage?
50% Answer Correctly
15
14
28
16

Solution

The mechanical advantage of a gear train is its gear ratio. The gear ratio (Vr) is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have three gears so the equation becomes:

Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{28}{14} \) \( \frac{14}{2} \) = \( \frac{28}{2} \) = 14


3

Power is the rate at which:

62% Answer Correctly

friction is overcome

potential energy is converted into kinetic energy

work is done

input force is transferred to output force


Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.


4 If you have a gear train with two gears, the first with 32 teeth and the second with 16 teeth, how many revolutions does the second gear make for each revolution of the first gear?
77% Answer Correctly
4
3.5
2
9

Solution

The gear ratio (Vr) of a gear train is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have only two gears so the equation becomes:

Vr = \( \frac{N_1}{N_2} \) = \( \frac{32}{16} \) = 2


5 If the green box weighs 35 lbs. and is 1 ft. from the fulcrum, how far from the fulcrum would a 55 lbs. force need to be applied to balance the lever?
58% Answer Correctly
1.27 ft.
0.64 ft.
0.16 ft.
0 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 db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{35 lbs. \times 1 ft.}{55 lbs.} \) = \( \frac{35 ft⋅lb}{55 lbs.} \) = 0.64 ft.