ASVAB Mechanical Comprehension Practice Test 379202 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.60
Score	0%	72%

Review

Coplanar forces:

62% Answer Correctly

	have opposite dimensions
	pass through a common point
	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.

2 What is the efficiency of a machine has work input of 190 ft⋅lb and work output of 104 ft⋅lb?

67% Answer Correctly

	220%
	110%
	55%
	27%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{104 ft⋅lb}{190 ft⋅lb} \times 100 \) \( = 55% \) %

A shovel is an example of which class of lever?

56% Answer Correctly

	a shovel is not a lever
	first
	second
	third

Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

An object's resistance to changes in direction is known as:

82% Answer Correctly

	mass
	kinetic energy
	inertia
	weight

Solution

The more mass a substance has the more force is required to move it or to change its direction. This resistance to changes in direction is known as inertia.

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

89% Answer Correctly

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

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.