ASVAB Mechanical Comprehension Practice Test 386129 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.20
Score	0%	64%

Review

1 If this lever is in equilibrium with an effort force of 8.33 ft. lb. at the blue arrow and a resistance force of 5 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	0.6
	1.8
	0.9
	3.6

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{5 ft.}{8.33 ft.} \) = 0.6

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.6 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.

2 If you lift a 30 lbs. rock 34 ft. from the ground, how much work have you done?

71% Answer Correctly

	None of these is correct
	2040 ft⋅lb
	510 ft⋅lb
	1020 ft⋅lb

Solution

Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 30 \times 34 \)
\( W = 1020 \)

Which of the following statements about drag is false?

58% Answer Correctly

	drag occurs during movement through a fluid
	the amount of drag depends on the speed of an object
	the amount of drag depends on the shape of an object
	slower objects experience more drag than faster objects

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.

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

89% Answer Correctly

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

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.

A fixed pulley is useful for which of the following?

53% Answer Correctly

	multiplying the input distance
	multiplying the input force
	changing the direction of the output force
	changing the direction of the input force

Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.