ASVAB Mechanical Comprehension Practice Test 880365 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.55
Score	0%	71%

Review

Which of these is the formula for kinetic energy?

68% Answer Correctly

	\(KE = mgh\)
	\(KE = {1 \over 2}mh^2\)
	\(KE = {m \over v^2 }\)
	\(KE = {1 \over 2}mv^2\)

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

2 50 lbs. of effort is used by a machine to lift a 300 lbs. box. What is the mechanical advantage of the machine?

84% Answer Correctly

	2
	6
	7.5
	9

Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{300 lbs.}{50 lbs.} \) = 6

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

80% Answer Correctly

	efficiency
	mechanical advantage
	work
	power

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.

4 What is the efficiency of a machine has work input of 230 ft⋅lb and work output of 103 ft⋅lb?

67% Answer Correctly

	180%
	45%
	2%
	55%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{103 ft⋅lb}{230 ft⋅lb} \times 100 \) \( = 45% \) %

A shovel is an example of which class of lever?

56% Answer Correctly

	third
	first
	a shovel is not a lever
	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.