ASVAB Mechanical Comprehension Practice Test 212957 Results

Your Results Global Average
Questions 5 5
Correct 0 3.37
Score 0% 67%

Review

1 If the handles of a wheelbarrow are 2.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 120 lbs. load concentrated at a point 1.5 ft. from the axle?
52% Answer Correctly
90
52.7
None of these is correct
240
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 effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{120 \times 1.5}{2.0} \)
\( F_e = \frac{180.0}{2.0} \)
\( F_e = 90 \)
2

Two or more pulleys used together are called:

71% Answer Correctly

block and tackle

gears

wheel and axle

third-class lever
Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement.  So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

3 If the green box weighs 65 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 8 ft.?
63% Answer Correctly
48.75 lbs.
97.5 lbs.
73.13 lbs.
24.38 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 = \( \frac{R_ad_a}{d_b} \) = \( \frac{65 lbs. \times 3 ft.}{8 ft.} \) = \( \frac{195 ft⋅lb}{8 ft.} \) = 24.38 lbs.

4

The mechanical advantage of a wheel and axle is equal to the:

61% Answer Correctly

difference in the lengths of the axles

length of the axle

ratio of the diameters of the wheels

difference in the diameters of the wheels
Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

5

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

wheel and axle

block and tackle

fixed pulley

first-class lever
Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.