ASVAB Mechanical Comprehension Practice Test 285622 Results

Your Results Global Average
Questions 5 5
Correct 0 2.49
Score 0% 50%

Review

1 If the green box weighs 50 lbs. and is 3 ft. from the fulcrum, how far from the fulcrum would a 10 lbs. force need to be applied to balance the lever?
58% Answer Correctly
0 ft.
16 ft.
60 ft.
15 ft.
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 db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{50 lbs. \times 3 ft.}{10 lbs.} \) = \( \frac{150 ft⋅lb}{10 lbs.} \) = 15 ft.

2

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

force or speed

force or distance

power or distance

speed or power
Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

3 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 200 lbs. force lift?
47% Answer Correctly
12
None of these is correct
200
-54.8
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:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{200 \times 1.0}{1.0} \)
\( F_r = \frac{200.0}{1.0} \)
\( F_r = 200 \)
4

Force of friction due to kinetic friction is __________ the force of friction due to static friction.

40% Answer Correctly

lower than

opposite

the same as

higher than
Solution

The formula for force of friction (Ff) is the same whether kinetic or static friction applies: Ff = μFN. To distinguish between kinetic and static friction, μk and μs are often used in place of μ.

5

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

60% Answer Correctly

difference in the lengths of the axles

difference in the diameters of the wheels

length of the axle

ratio of 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.