ASVAB Mechanical Comprehension Practice Test 54175 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.41
Score	0%	68%

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

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

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.

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

62% Answer Correctly

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

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).

3 If the green box weighs 50 lbs. and 65 lbs. of force is applied 3 ft. from the fulcrum at the blue arrow, how far from the fulcrum would the green box need to be placed to balance the lever?

55% Answer Correctly

	150 ft.
	3.9 ft.
	0.98 ft.
	15.6 ft.

Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

Solving for d_a, our missing value, and plugging in our variables yields:

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{65 lbs. \times 3 ft.}{50 lbs.} \) = \( \frac{195 ft⋅lb}{50 lbs.} \) = 3.9 ft.

When all forces acting on a system cancel each other out, this is called:

81% Answer Correctly

	potential energy
	equilibrium
	stasis
	rest

Solution

When a system is stable or balanced (equilibrium) all forces acting on the system cancel each other out. In the case of torque, equilibrium means that the sum of the anticlockwise moments about a center of rotation equal the sum of the clockwise moments.

Potential energy is energy that has the potential to be converted into what?

81% Answer Correctly

	work
	power
	heat
	kinetic energy

Solution

Potential energy is the energy of an object by virtue of its position relative to other objects. It is energy that has the potential to be converted into kinetic energy.