ASVAB Mechanical Comprehension Practice Test 49682 Results

Your Results Global Average
Questions 5 5
Correct 0 3.01
Score 0% 60%

Review

1 If a 65 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow and the green box is 8 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
24.38 lbs.
6.09 lbs.
8.13 lbs.
48.75 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 = \( \frac{R_bd_b}{d_a} \) = \( \frac{65 lbs. \times 3 ft.}{8 ft.} \) = \( \frac{195 ft⋅lb}{8 ft.} \) = 24.38 lbs.


2 If the green box weighs 50 lbs. and is 3 ft. from the fulcrum, how much weight would need to be placed at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 2 ft.?
63% Answer Correctly
37.5 lbs.
300 lbs.
0 lbs.
75 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 Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{50 lbs. \times 3 ft.}{2 ft.} \) = \( \frac{150 ft⋅lb}{2 ft.} \) = 75 lbs.


3

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

65% Answer Correctly

energy

rotational direction

force

torque


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.


4

For any given surface, the coefficient of static friction is ___________ the coefficient of kinetic friction.

54% Answer Correctly

equal to

opposite

higher than

lower 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

Boyle's law defines the relationship between pressure and volume as:

58% Answer Correctly

\(\frac{P_1}{P_2} = {V_1}{V_2}\)

\(\frac{P_1}{P_2} = \frac{V_1}{V_2}\)

\({P_1}{P_2} = {V_1}{V_2}\)

\(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)


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". Expressed as a formula, that's \(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)