ASVAB Mechanical Comprehension Practice Test 998347 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.84
Score	0%	57%

Review

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

	output distance
	output force
	input force
	position of the fulcrum

Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

2 A 260 lb. barrel is rolled up a 12 ft. ramp to a platform that's 4 ft. tall. What effort is required to move the barrel?

53% Answer Correctly

	43.3 lbs.
	260 lbs.
	86.7 lbs.
	95.3 lbs.

Solution

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

F_ed_e = F_rd_r

Plugging in the variables from this problem yields:

F_e x 12 ft. = 260 lbs. x 4 ft.
F_e = \( \frac{1040 ft⋅lb}{12 ft.} \) = 86.7 lbs.

Which of the following is not true of a first-class lever?

51% Answer Correctly

	increases force
	decreases distance
	changes the direction of force
	increases distance

Solution

Power is the rate at which:

62% Answer Correctly

	friction is overcome
	input force is transferred to output force
	work is done
	potential energy is converted into kinetic energy

Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

	its weight
	its speed
	its direction
	its mass

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.