ASVAB Mechanical Comprehension Practice Test 399327 Results

Your Results Global Average
Questions 5 5
Correct 0 2.98
Score 0% 60%

Review

1 If the green box weighs 35 lbs. and is 8 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 9 ft.?
62% Answer Correctly
93.33 lbs.
31.11 lbs.
124.44 lbs.
7.78 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 = \( \frac{R_ad_a}{d_b} \) = \( \frac{35 lbs. \times 8 ft.}{9 ft.} \) = \( \frac{280 ft⋅lb}{9 ft.} \) = 31.11 lbs.

2

The science that deals with motion and the forces that produce motion is called which of the following?

57% Answer Correctly

mechanics

physics

engineering

aeronautics
Solution

Mechanics deals with motion and the forces that produce motion.

3

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

54% Answer Correctly

opposite

equal to

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).

4

Normal force is generally equal to the __________ of an object.

61% Answer Correctly

weight

mass

coefficient of friction

density
Solution

Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.

5 A = 9 ft., the green box weighs 20 lbs., and the blue box weighs 65 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
585 ft.
0.92 ft.
2.77 ft.
2 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:

20 lbs. x 9 ft. = 65 lbs. x dB

dB = \( \frac{20 \times 9 ft⋅lb}{65 lbs.} \) = \( \frac{180 ft⋅lb}{65 lbs.} \) = 2.77 ft.