ASVAB Mechanical Comprehension Practice Test 74301 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.27
Score	0%	65%

Review

1 If the handles of a wheelbarrow are 1.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 240 lbs. load concentrated at a point 1.5 ft. from the axle?

52% Answer Correctly

	1
	26.6
	240
	106.7

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. In this problem we're looking for effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{240 \times 1.5}{1.5} \)
\( F_e = \frac{360.0}{1.5} \)
\( F_e = 240 \)

Tension is a force that does which of the following?

75% Answer Correctly

	heats up an object
	compacts an object
	slows an object
	stretches an object

Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.

3 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

	0.9
	0.54
	1.2
	0.6

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.

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

70% Answer Correctly

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

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

80% Answer Correctly

	efficiency
	mechanical advantage
	power
	work

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.