ASVAB Mechanical Comprehension Practice Test 543011 Results

Your Results Global Average
Questions 5 5
Correct 0 3.25
Score 0% 65%

Review

1

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

65% Answer Correctly

rotational direction

torque

force

energy
Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

2

A watt is the unit for which of the following?

71% Answer Correctly

energy

power

work

mechanical advantage
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.

3

A screw is most like which of the following other simple machines?

50% Answer Correctly

first-class lever

block and tackle

inclined plane

wheel and axle
Solution

A screw is an inclined plane wrapped in ridges (threads) around a cylinder. The distance between these ridges defines the pitch of the screw and this distance is how far the screw advances when it is turned once. The mechanical advantage of a screw is its circumference divided by the pitch.

4 If A = 6 ft. and the green box weighs 45 lbs. what is the torque acting on the A side of this lever?
74% Answer Correctly
810 ft⋅lb
1080 ft⋅lb
270 ft⋅lb
135 ft⋅lb
Solution
For a lever, torque is weight x distance from the fulcrum which, in this case, is: 45 ft. x 6 lbs. = 270 ft⋅lb
5 A = 5 ft., the green box weighs 30 lbs., and the blue box weighs 80 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
7.5 ft.
400 ft.
1.88 ft.
3.75 ft.
Solution
In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB

For this problem, the equation becomes:

30 lbs. x 5 ft. = 80 lbs. x dB

dB = \( \frac{30 \times 5 ft⋅lb}{80 lbs.} \) = \( \frac{150 ft⋅lb}{80 lbs.} \) = 1.88 ft.