ASVAB Mechanical Comprehension Practice Test 562102 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.26
Score	0%	65%

Review

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

80% Answer Correctly

	power
	work
	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.

2 A = 4 ft., the green box weighs 50 lbs., and the blue box weighs 70 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	1.43 ft.
	0.95 ft.
	2.86 ft.
	17 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B

For this problem, the equation becomes:

50 lbs. x 4 ft. = 70 lbs. x d_B

d_B = \( \frac{50 \times 4 ft⋅lb}{70 lbs.} \) = \( \frac{200 ft⋅lb}{70 lbs.} \) = 2.86 ft.

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

61% Answer Correctly

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

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).

A wedge converts force applied to its blunt end into force __________ its inclined surface.

57% Answer Correctly

	along
	perpendicular to
	opposite to
	parallel to

Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

5 If the green box weighs 65 lbs. and is 6 ft. from the fulcrum, how much force would need to be applied at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 8 ft.?

62% Answer Correctly

	16.25 lbs.
	48.75 lbs.
	12.19 lbs.
	146.25 lbs.

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 R_b, our missing value, and plugging in our variables yields:

R_b = \( \frac{R_ad_a}{d_b} \) = \( \frac{65 lbs. \times 6 ft.}{8 ft.} \) = \( \frac{390 ft⋅lb}{8 ft.} \) = 48.75 lbs.