ASVAB Mechanical Comprehension Practice Test 18820 Results

Your Results Global Average
Questions 5 5
Correct 0 3.35
Score 0% 67%

Review

1 If A = 10 ft., B = 1 ft., C = 6 ft., the green box weighs 25 lbs. and the blue box weighs 35 lbs., what does the orange box have to weigh for this lever to balance?
43% Answer Correctly
107.5 lbs.
17.92 lbs.
11.94 lbs.
35.83 lbs.
Solution
In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB + fCdC

For this problem, this equation becomes:

25 lbs. x 10 ft. = 35 lbs. x 1 ft. + fC x 6 ft.

250 ft. lbs. = 35 ft. lbs. + fC x 6 ft.

fC = \( \frac{250 ft. lbs. - 35 ft. lbs.}{6 ft.} \) = \( \frac{215 ft. lbs.}{6 ft.} \) = 35.83 lbs.

2 If A = 3 ft. and the green box weighs 10 lbs. what is the torque acting on the A side of this lever?
75% Answer Correctly
15 ft⋅lb
7 ft⋅lb
60 ft⋅lb
30 ft⋅lb
Solution
For a lever, torque is weight x distance from the fulcrum which, in this case, is: 10 ft. x 3 lbs. = 30 ft⋅lb
3 If you have a gear train with two gears, the first with 28 teeth and the second with 12 teeth, how many revolutions does the second gear make for each revolution of the first gear?
77% Answer Correctly
3.8
2.6
-6.7
2.3
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 = \( \frac{N_1}{N_2} \) = \( \frac{28}{12} \) = 2.3

4

Tension is a force that does which of the following?

75% Answer Correctly

compacts an object

stretches an object

slows an object

heats up an object
Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.

5

The mechanical advantage of a wheel and axle is equal to the:

61% Answer Correctly

difference in the diameters of the wheels

ratio of the diameters of the wheels

length of the axle

difference in the lengths of the axles
Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.