ASVAB Mechanical Comprehension Practice Test 355238 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.21
Score	0%	64%

Review

A shovel is an example of which class of lever?

57% Answer Correctly

	third
	second
	first
	a shovel is not a lever

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.

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

	power or distance
	speed or power
	force or distance
	force or speed

Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

66% Answer Correctly

	rotational direction
	force
	energy
	torque

Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

4 If you lift a 37 lbs. rock 16 ft. from the ground, how much work have you done?

72% Answer Correctly

	None of these is correct
	592 ft⋅lb
	21 ft⋅lb
	288 ft⋅lb

Solution

Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 37 \times 16 \)
\( W = 592 \)

5 How much resistance could a 115 lb. effort force lift using a block and tackle pulley that has 4 ropes supporting the resistance?

82% Answer Correctly

	463 lbs.
	460 lbs.
	461.5 lbs.
	153 lbs.

Solution

The mechanical advantage (MA) of a block and tackle pulley is equal to the number of times the effort force changes direction. An easy way to count how many times the effort force changes direction is to count the number of ropes that support the resistance which, in this problem, is 4. With a MA of 4, a 115 lbs. effort force could lift 115 lbs. x 4 = 460 lbs. resistance.