ASVAB Mechanical Comprehension Practice Test 767785 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.53
Score	0%	71%

Review

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	first
	third
	none of these, all levers offer mechanical advantage
	second

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.

When all forces acting on a system cancel each other out, this is called:

80% Answer Correctly

	equilibrium
	rest
	stasis
	potential energy

Solution

When a system is stable or balanced (equilibrium) all forces acting on the system cancel each other out. In the case of torque, equilibrium means that the sum of the anticlockwise moments about a center of rotation equal the sum of the clockwise moments.

Friction between two or more solid objects that are not moving relative to each other is called:

73% Answer Correctly

	static friction
	kinetic friction
	dynamic friction
	gravitational friction

Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.

4 What is the efficiency of a machine has work input of 155 ft⋅lb and work output of 147 ft⋅lb?

67% Answer Correctly

	95%
	0%
	23%
	5%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{147 ft⋅lb}{155 ft⋅lb} \times 100 \) \( = 95% \) %

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

81% Answer Correctly

	inertia
	kinetic energy
	mass
	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.