ASVAB Mechanical Comprehension Practice Test 722451 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.14
Score	0%	63%

Review

Which of the following statements about drag is false?

58% Answer Correctly

	slower objects experience more drag than faster objects
	the amount of drag depends on the speed of an object
	the amount of drag depends on the shape of an object
	drag occurs during movement through a fluid

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

63% Answer Correctly

	density, volume
	pressure, volume
	pressure, density
	volume, mass

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".

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

	position of the fulcrum
	output distance
	output force
	input 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.

Coplanar forces:

61% Answer Correctly

	act along the same line of action
	have opposite dimensions
	pass through a common point
	act in a common plane

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.

5 What is the efficiency of a machine has work input of 225 ft⋅lb and work output of 112 ft⋅lb?

67% Answer Correctly

	25%
	12%
	50%
	0%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{112 ft⋅lb}{225 ft⋅lb} \times 100 \) \( = 50% \) %