ASVAB Mechanical Comprehension Practice Test 873709 Results

Your Results Global Average
Questions 5 5
Correct 0 3.14
Score 0% 63%

Review

1 A = 7 ft., the green box weighs 15 lbs., and the blue box weighs 65 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
4.85 ft.
1.62 ft.
6.46 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:

15 lbs. x 7 ft. = 65 lbs. x dB

dB = \( \frac{15 \times 7 ft⋅lb}{65 lbs.} \) = \( \frac{105 ft⋅lb}{65 lbs.} \) = 1.62 ft.

2

Which class of lever offers no mechanical advantage?

45% Answer Correctly

second

none of these, all levers offer mechanical advantage

first

third
Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

3

Hydraulics is the transmission of force through the use of which of the following?

73% Answer Correctly

air pressure

torque

liquids

gear systems
Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).

4 If the handles of a wheelbarrow are 1.0 ft. from the wheel axle and the load is concentrated at a point 1.0 ft. from the axle, how many pounds of load will a 120 lbs. force lift?
47% Answer Correctly
0
-37.9
118.5
120
Solution
This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: Fede = Frdr. In this problem we're looking for resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{120 \times 1.0}{1.0} \)
\( F_r = \frac{120.0}{1.0} \)
\( F_r = 120 \)
5 What's the mechanical advantage of a wedge that's 5 inches wide and 45 inches long?
83% Answer Correctly
5
4
10.5
9
Solution

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{45 in.}{5 in.} \) = 9