ASVAB Mechanical Comprehension Practice Test 116353 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.78
Score	0%	56%

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
	drag occurs during movement through a fluid
	the amount of drag depends on the shape of an object

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.

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

45% Answer Correctly

	potential energy
	acceleration
	total mechanical energy
	kinetic energy

Solution

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

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

48% Answer Correctly

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

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.

4 What is the efficiency of a machine has work input of 115 ft⋅lb and work output of 51 ft⋅lb?

67% Answer Correctly

	2%
	22%
	45%
	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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{51 ft⋅lb}{115 ft⋅lb} \times 100 \) \( = 45% \) %

Coplanar forces:

62% Answer Correctly

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

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.