ASVAB Mechanical Comprehension Practice Test 608648 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.99
Score	0%	60%

Review

1 A 220 lb. barrel is rolled up a 7 ft. ramp to a platform that's 1 ft. tall. What effort is required to move the barrel?

53% Answer Correctly

	31.4 lbs.
	15.7 lbs.
	47.1 lbs.
	33.4 lbs.

Solution

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

F_ed_e = F_rd_r

Plugging in the variables from this problem yields:

F_e x 7 ft. = 220 lbs. x 1 ft.
F_e = \( \frac{220 ft⋅lb}{7 ft.} \) = 31.4 lbs.

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

	810 lbs
	45 lbs
	0.83 lbs
	90 lbs

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: F_ed_e = F_rd_r. Plugging in the variables from this problem yields:

F_e x 3 ft. = 270 lbs x 0.5 ft
F_e = 135 ft-lb. / 3 ft
F_e= 45 lbs

3 What is the power output of a 5 hp engine that's 45% efficient?

40% Answer Correctly

	9 \( \frac{ft⋅lb}{s} \)
	3712.5 \( \frac{ft⋅lb}{s} \)
	1237.5 \( \frac{ft⋅lb}{s} \)
	412.5 \( \frac{ft⋅lb}{s} \)

Solution

\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), P_i becomes 5 hp x 550 \( \frac{ft⋅lb}{s} \) = 2750 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{45 \times 2750 \frac{ft⋅lb}{s}}{100} \) \( = \frac{123750 \frac{ft⋅lb}{s}}{100} \) = 1237.5 \( \frac{ft⋅lb}{s} \)

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

89% Answer Correctly

	block and tackle
	first-class lever
	wheel and axle
	fixed pulley

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.

An inclined plane increases ___________ to reduce ____________.

58% Answer Correctly

	force, power
	distance, force
	distance, power
	force, distance

Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.