ASVAB Mechanical Comprehension Practice Test 405101 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.70
Score	0%	54%

Review

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	second
	third
	first
	none of these, all levers offer mechanical advantage

Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

Which of the following is not a modulus of elasticity?

47% Answer Correctly

	bulk modulus
	stress modulus
	stretch modulus
	shear modulus

Solution

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).

3 If A = 11 ft., B = 1 ft., C = 10 ft., the green box weighs 35 lbs. and the blue box weighs 40 lbs., what does the orange box have to weigh for this lever to balance?

44% Answer Correctly

	34.5 lbs.
	3 lbs.
	103.5 lbs.
	17.25 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:

35 lbs. x 11 ft. = 40 lbs. x 1 ft. + f_C x 10 ft.

385 ft. lbs. = 40 ft. lbs. + f_C x 10 ft.

f_C = \( \frac{385 ft. lbs. - 40 ft. lbs.}{10 ft.} \) = \( \frac{345 ft. lbs.}{10 ft.} \) = 34.5 lbs.

4 If you lift a 42 lbs. rock 17 ft. from the ground, how much work have you done?

70% Answer Correctly

	25 ft⋅lb
	714 ft⋅lb
	0 ft⋅lb
	None of these is correct

Solution

Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 42 \times 17 \)
\( W = 714 \)

Normal force is generally equal to the __________ of an object.

61% Answer Correctly

	coefficient of friction
	mass
	weight
	density

Solution

Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.