ASVAB Mechanical Comprehension Practice Test 819350 Results

Your Results Global Average
Questions 5 5
Correct 0 3.09
Score 0% 62%

Review

1

A fixed pulley is useful for which of the following?

53% Answer Correctly

multiplying the input distance

changing the direction of the output force

changing the direction of the input force

multiplying the input force


Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.


2 If a 60 lbs. weight is placed 1 ft. from the fulcrum at the blue arrow and the green box is 6 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
30 lbs.
10 lbs.
5 lbs.
0 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 Ra, our missing value, and plugging in our variables yields:

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{60 lbs. \times 1 ft.}{6 ft.} \) = \( \frac{60 ft⋅lb}{6 ft.} \) = 10 lbs.


3

An inclined plane increases ___________ to reduce ____________.

58% Answer Correctly

distance, force

distance, power

force, distance

force, power


Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.


4 If A = 9 ft. and the green box weighs 40 lbs. what is the torque acting on the A side of this lever?
74% Answer Correctly
1440 ft⋅lb
120 ft⋅lb
360 ft⋅lb
4 ft⋅lb

Solution
For a lever, torque is weight x distance from the fulcrum which, in this case, is: 40 ft. x 9 lbs. = 360 ft⋅lb

5

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

61% Answer Correctly

increase, decrease

increase, increase

decrease, increase

decrease, decrease


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.