ASVAB Mechanical Comprehension Practice Test 598285 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.93
Score	0%	59%

Review

Force of friction due to kinetic friction is __________ the force of friction due to static friction.

41% Answer Correctly

	the same as
	lower than
	higher than
	opposite

Solution

The formula for force of friction (F_f) is the same whether kinetic or static friction applies: F_{f =}μF_N. To distinguish between kinetic and static friction, μ_k and μ_s are often used in place of μ.

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

61% Answer Correctly

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

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).

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

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

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.

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

	0
	1
	2
	4

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

5 If A = 8 ft., B = 2 ft., C = 4 ft., the green box weighs 45 lbs. and the blue box weighs 60 lbs., what does the orange box have to weigh for this lever to balance?

43% Answer Correctly

	60 lbs.
	360 lbs.
	180 lbs.
	15 lbs.

Solution

In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. 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 + f_Cd_C

For this problem, this equation becomes:

45 lbs. x 8 ft. = 60 lbs. x 2 ft. + f_C x 4 ft.

360 ft. lbs. = 120 ft. lbs. + f_C x 4 ft.

f_C = \( \frac{360 ft. lbs. - 120 ft. lbs.}{4 ft.} \) = \( \frac{240 ft. lbs.}{4 ft.} \) = 60 lbs.