ASVAB Mechanical Comprehension Practice Test 387508 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.43
Score	0%	69%

Review

The force amplification achieved by using a tool, mechanical device or machine system is called:

80% Answer Correctly

	power
	work
	mechanical advantage
	efficiency

Solution

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Such a device utilizes input force and trades off forces against movement to amplify and/or change its direction.

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

	second-class lever
	third-class lever
	inclined plane
	first-class lever

Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

3 If the green box is 7 ft. from the fulcrum and a certain force applied 6 ft. from the fulcrum at the blue arrow balances the lever, what is the mechanical advantage?

60% Answer Correctly

	1.29
	2.86
	0.86
	2.57

Solution

Because this lever is in equilibrium, we know that the effort force at the blue arrow is equal to the resistance weight of the green box. For a lever that's in equilibrium, one method of calculating mechanical advantage (MA) is to divide the length of the effort arm (E_a) by the length of the resistance arm (R_a):

MA = \( \frac{E_a}{R_a} \) = \( \frac{6 ft.}{7 ft.} \) = 0.86

When a lever is in equilibrium, the torque from the effort and the resistance are equal. The equation for equilibrium is R_ad_a = R_bd_b where a and b are the two points at which effort/resistance is being applied to the lever.

In this problem, R_a and R_b are such that the lever is in equilibrium meaning that some multiple of the weight of the green box is being applied at the blue arrow. For a lever, this multiple is a function of the ratio of the distances of the box and the arrow from the fulcrum. That's why, for a lever in equilibrium, only the distances from the fulcrum are necessary to calculate mechanical advantage.

If the lever were not in equilibrium, you would first have to calculate the forces and distances necessary to put it in equilibrium and then divide E_a by R_a to get the mechanical advantage.

Collinear forces:

72% Answer Correctly

	are unrelated to each other
	act along the same line of action
	act in a common plane
	pass through a common point

Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

Two gears are connected and the larger gear drives the smaller gear. The speed of rotation will __________ and the torque will __________.

61% Answer Correctly

	increase, decrease
	decrease, decrease
	increase, increase
	decrease, increase

Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.