ASVAB Mechanical Comprehension Practice Test 798703 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.42
Score	0%	68%

Review

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

	position of the fulcrum
	input force
	output distance
	output force

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.

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

67% Answer Correctly

	the object's weight
	gravity
	the object's density
	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.

The measure of how much of the power put into a machine is turned into movement or force is called:

56% Answer Correctly

	force multiplication
	efficiency
	power
	mechanical advantage

Solution

The efficiency of a machine describes how much of the power put into the machine is turned into movement or force. A 100% efficient machine would turn all of the input power into output movement or force. However, no machine is 100% efficient due to friction, heat, wear and other imperfections that consume input power without delivering any output.

4 If the green arrow in this diagram represents 260 ft⋅lb of work, how far will the box move if it weighs 130 pounds?

73% Answer Correctly

	2 ft.
	260 ft.
	1 ft.
	520 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 260 ft⋅lb and the resistance force is 130 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
260 ft⋅lb = 130 lbs. x d_resistance
d_resistance = \( \frac{260ft⋅lb}{130 lbs.} \) = 2 ft.

5 How much resistance could a 125 lb. effort force lift using a block and tackle pulley that has 10 ropes supporting the resistance?

82% Answer Correctly

	1125 lbs.
	1250 lbs.
	1252 lbs.
	3750 lbs.

Solution

The mechanical advantage (MA) of a block and tackle pulley is equal to the number of times the effort force changes direction. An easy way to count how many times the effort force changes direction is to count the number of ropes that support the resistance which, in this problem, is 10. With a MA of 10, a 125 lbs. effort force could lift 125 lbs. x 10 = 1250 lbs. resistance.