ASVAB Mechanical Comprehension Practice Test 303361 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.24
Score	0%	65%

Review

1 If you have a gear train with two gears, the first with 24 teeth and the second with 12 teeth, how many revolutions does the second gear make for each revolution of the first gear?

77% Answer Correctly

	3
	0.7
	2
	5

Solution

The gear ratio (V_r) of a gear train 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 only two gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) = \( \frac{24}{12} \) = 2

2 If A = 2 ft. and the green box weighs 40 lbs. what is the torque acting on the A side of this lever?

75% Answer Correctly

	240 ft⋅lb
	20 ft⋅lb
	0 ft⋅lb
	80 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 40 ft. x 2 lbs. = 80 ft⋅lb

A fixed pulley is useful for which of the following?

54% Answer Correctly

	multiplying the input distance
	changing the direction of the input force
	multiplying the input force
	changing the direction of the output force

Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

A shovel is an example of which class of lever?

56% Answer Correctly

	a shovel is not a lever
	third
	first
	second

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 the formula for torque?

61% Answer Correctly

	τ = rF
	τ = F/r
	τ = r/F
	τ = F/r²

Solution

Torque measures force applied during rotation: τ = rF. Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).