ASVAB Mechanical Comprehension Practice Test 692013 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.22
Score	0%	64%

Review

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

60% Answer Correctly

	mechanical advantage
	Pascal's law
	conservation of mechanical energy
	work-energy theorem

Solution

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.

The force exerted on an object due to gravity is called:

70% Answer Correctly

	mass
	density
	potential energy
	weight

Solution

Mass is an intrinsic property of matter and does not vary. Weight is the force exerted on the mass of an object due to gravity and a specific case of Newton's Second Law of Motion. Replace force with weight and acceleration with acceleration due to gravity on Earth (g) and the result is the formula for weight: W = mg or, substituting for g, weight equals mass multiplied by 9.8 m/s².

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

66% Answer Correctly

	energy
	rotational direction
	force
	torque

Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

4 What is the efficiency of a machine has work input of 155 ft⋅lb and work output of 62 ft⋅lb?

67% Answer Correctly

	10%
	160%
	40%
	60%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{62 ft⋅lb}{155 ft⋅lb} \times 100 \) \( = 40% \) %

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
	power
	efficiency
	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.