ASVAB Mechanical Comprehension Practice Test 931606 Results

Your Results Global Average
Questions 5 5
Correct 0 2.99
Score 0% 60%

Review

1 If the green box weighs 75 lbs. and is 5 ft. from the fulcrum, how much force would need to be applied at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 8 ft.?
62% Answer Correctly
600 lbs.
46.88 lbs.
23.44 lbs.
11.72 lbs.

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 Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{75 lbs. \times 5 ft.}{8 ft.} \) = \( \frac{375 ft⋅lb}{8 ft.} \) = 46.88 lbs.


2

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

63% Answer Correctly

volume, mass

pressure, volume

density, volume

pressure, density


Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional".


3

The mechanical advantage of a third class lever is always:

37% Answer Correctly

equal to one

not equal to one

less than one

greater than one


Solution

A third class lever is designed to multiply distance and speed at the expense of effort force. Because the effort force is greater than the resistance, the mechanical advantage of a third class lever is always less than one.

An example of a third class lever is a broom. The fulcrum is at your hand on the end of the broom, the effort force is your other hand in the middle, and the resistance is at the bottom bristles. The effort force of your hand in the middle multiplies the distance and speed of the bristles at the bottom but at the expense of producing a brushing force that's less than the force you're applying with your hand.


4

The force required to initally get an object moving is __________ the force required to keep it moving. 

76% Answer Correctly

lower than

the same as

opposite

higher than


Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).


5

Which of the following will increase the mechanical advantage of this inclined plane?

58% Answer Correctly

increase the force acting at the blue arrow

lower the force acting at the blue arrow

shorten the ramp

lengthen the ramp


Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In order to increase mechanical advantage, this ratio must increase which means making the effort distance longer and this can be accomplished by lengthening the length of the ramp.