ASVAB Mechanical Comprehension Practice Test 969703 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.02
Score	0%	60%

Review

1 What is the efficiency of a machine has work input of 130 ft⋅lb and work output of 39 ft⋅lb?

67% Answer Correctly

	120%
	3%
	30%
	60%

Solution

Due to friction, a machine will never be able to utilize 100% of its work input. A certain percentage of that input will be lost in overcoming friction within the machine. Effeciency is a measure of how much of a machine's work input can be turned into useful work output and is calculated by dividing work output by work input and multiplying the result by 100:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{39 ft⋅lb}{130 ft⋅lb} \times 100 \) \( = 30% \) %

What is work?

60% Answer Correctly

	Force per unit time
	The potential for exertion
	Force per unit distance
	The movement of an object by a force

Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.

Concurrent forces:

55% Answer Correctly

	pass through a common point
	act in a common dimension
	act along the same line of action
	act in a common plane

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.

The mass of an object correlates to the size of the object but ultimately depends on:

66% Answer Correctly

	gravity
	the object's density
	the object's weight
	the object's potential energy

Solution

Mass is a measure of the amount of matter in an object. In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

Which class of lever is used to increase force on an object in the same direction as the force is applied?

52% Answer Correctly

	first
	all of these
	second
	third

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.