ASVAB Mechanical Comprehension Practice Test 758595 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.31
Score	0%	66%

Review

1 If you have a gear train with three gears, the first with 30 teeth, the second with 12 teeth, and the third with 8 teeth, what is its mechanical advantage?

51% Answer Correctly

	3.8
	6.8
	5.8
	3.4

Solution

The mechanical advantage of a gear train is its gear ratio. The gear ratio (V_r) is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have three gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{30}{12} \) \( \frac{12}{8} \) = \( \frac{30}{8} \) = 3.8

Which of the following will increase the mechanical advantage of this inclined plane?

58% Answer Correctly

	increase the force acting at the blue arrow
	lower the force acting at the blue arrow
	lengthen the ramp
	shorten the ramp

Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In order to increase mechanical advantage, this ratio must increase which means making the effort distance longer and this can be accomplished by lengthening the length of the ramp.

3 If A = 7 ft. and the green box weighs 35 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	5 ft⋅lb
	490 ft⋅lb
	245 ft⋅lb
	735 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 35 ft. x 7 lbs. = 245 ft⋅lb

Which of the following surfaces would have the highest coefficient of friction?

77% Answer Correctly

	marble
	concrete
	steel
	ice

Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

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

70% Answer Correctly

	first-class lever
	inclined plane
	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.