ASVAB Mechanical Comprehension Practice Test 3044 Results

Your Results Global Average
Questions 5 5
Correct 0 3.41
Score 0% 68%

Review

1

Which of the following surfaces would have the highest coefficient of friction?

77% Answer Correctly

steel

marble

concrete

ice
Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other.  Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

2 If a 55 lbs. weight is placed 9 ft. from the fulcrum at the blue arrow and the green box is 4 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
123.75 lbs.
41.25 lbs.
30.94 lbs.
61.88 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 = \( \frac{R_bd_b}{d_a} \) = \( \frac{55 lbs. \times 9 ft.}{4 ft.} \) = \( \frac{495 ft⋅lb}{4 ft.} \) = 123.75 lbs.

3

An object's resistance to changes in direction is known as:

82% Answer Correctly

kinetic energy

mass

inertia

weight
Solution

The more mass a substance has the more force is required to move it or to change its direction. This resistance to changes in direction is known as inertia.

4 A = 4 ft., the green box weighs 10 lbs., and the blue box weighs 45 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
3.56 ft.
2.67 ft.
0.89 ft.
0.22 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:

10 lbs. x 4 ft. = 45 lbs. x dB

dB = \( \frac{10 \times 4 ft⋅lb}{45 lbs.} \) = \( \frac{40 ft⋅lb}{45 lbs.} \) = 0.89 ft.

5

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

50% Answer Correctly

first-class lever

block and tackle

inclined plane

wheel and axle
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.