ASVAB Mechanical Comprehension Practice Test 746637 Results

Your Results Global Average
Questions 5 5
Correct 0 3.16
Score 0% 63%

Review

1 If the green box weighs 20 lbs. and is 3 ft. from the fulcrum, how far from the fulcrum would a 45 lbs. weight need to be placed to balance the lever?
61% Answer Correctly
0.44 ft.
0.33 ft.
1.33 ft.
6 ft.
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 db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{20 lbs. \times 3 ft.}{45 lbs.} \) = \( \frac{60 ft⋅lb}{45 lbs.} \) = 1.33 ft.

2

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

50% Answer Correctly

wheel and axle

inclined plane

block and tackle

first-class lever
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.

3

Which of the following is not a type of bridge?

74% Answer Correctly

truss

block

cable

arch
Solution

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.

4

Two gears are connected and the larger gear drives the smaller gear. The speed of rotation will __________ and the torque will __________.

61% Answer Correctly

increase, decrease

decrease, increase

decrease, decrease

increase, increase
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.

5 If you lift a 40 lbs. rock 29 ft. from the ground, how much work have you done?
71% Answer Correctly
2320 ft⋅lb
11 ft⋅lb
1 ft⋅lb
1160 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 40 \times 29 \)
\( W = 1160 \)