ASVAB Mechanical Comprehension Practice Test 395764 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.17
Score	0%	63%

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?

61% Answer Correctly

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

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.

A a seesaw / teeter-totter is an example of which of the following?

70% Answer Correctly

	third-class lever
	second-class lever
	inclined plane
	first-class lever

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.

3 A mass of air has a pressure of 12.0 psi and a volume of 60 ft.³. If the air is compressed to a new volume of 40 ft.³, what is the new pressure?

57% Answer Correctly

	18 psi
	16.2 psi
	19.8 psi
	19.5 psi

Solution

According to Boyle's Law, pressure and volume are inversely proportional:

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

In this problem, V₂ = 40 ft.³, V₁ = 60 ft.³ and P₁ = 12.0 psi. Solving for P₂:

P₂ = \( \frac{P_1}{\frac{V_2}{V_1}} \) = \( \frac{12.0 psi}{\frac{40 ft.^3}{60 ft.^3}} \) = 18 psi

4 If the green arrow in this diagram represents 690 ft⋅lb of work, how far will the box move if it weighs 230 pounds?

73% Answer Correctly

	115 ft.
	3 ft.
	460 ft.
	12 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 690 ft⋅lb and the resistance force is 230 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
690 ft⋅lb = 230 lbs. x d_resistance
d_resistance = \( \frac{690ft⋅lb}{230 lbs.} \) = 3 ft.

Which of the following is the formula for gravitational potential energy?

62% Answer Correctly

	\(PE = mgh\)
	\(PE = mg^2h\)
	\(PE = { 1 \over 2} mg^2\)
	\(PE = { 1 \over 2} mv^2\)

Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s²).