ASVAB Mechanical Comprehension Practice Test 705461 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.90
Score	0%	58%

Review

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

	position of the fulcrum
	output force
	input force
	output distance

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.

Boyle's law defines the relationship between pressure and volume as:

57% Answer Correctly

	\(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)
	\({P_1}{P_2} = {V_1}{V_2}\)
	\(\frac{P_1}{P_2} = {V_1}{V_2}\)
	\(\frac{P_1}{P_2} = \frac{V_1}{V_2}\)

Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional". Expressed as a formula, that's \(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

Concurrent forces:

55% Answer Correctly

	act in a common dimension
	pass through a common point
	act in a common plane
	act along the same line of action

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.

4 What is the efficiency of a machine has work input of 125 ft⋅lb and work output of 106 ft⋅lb?

67% Answer Correctly

	1%
	340%
	85%
	170%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{106 ft⋅lb}{125 ft⋅lb} \times 100 \) \( = 85% \) %

Which of the following statements about this pulley configuration is false?

48% Answer Correctly

	Mechanical advantage is the number of ropes that support the resistance
	Only multiplies the effort force
	Changes the direction of and multiplies the effort force
	This is a block and tackle pulley configuration

Solution

A block and tackle is a combination of one or more fixed pulleys and one or more movable pulleys where the fixed pulleys change the direction of the effort force and the movable pulleys multiply it. The mechanical advantage is equal to the number of times the effort force changes direction and can be increased by adding more pulley wheels to the system. An easy way to find the mechanical advantage of a block and tackle pulley system is to count the number of ropes that support the resistance.