ASVAB Mechanical Comprehension Practice Test 4839 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.87
Score	0%	77%

Review

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

	first-class lever
	block and tackle
	fixed pulley
	wheel and axle

Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

	input force
	output force
	position of the fulcrum
	output distance

Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

3 What is the mechanical advantage of this inclined plane if the length of the ramp is 6 ft. and the height of the green box is 3 ft.?

82% Answer Correctly

	2
	5
	3.5
	1.8

Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:

MA = \( \frac{d_e}{d_r} \) = \( \frac{6 ft.}{3 ft.} \) = 2

4 If A = 2 ft. and the green box weighs 10 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	60 ft⋅lb
	20 ft⋅lb
	40 ft⋅lb
	0 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 10 ft. x 2 lbs. = 20 ft⋅lb

5 If you have a gear train with two gears, the first with 32 teeth and the second with 16 teeth, how many revolutions does the second gear make for each revolution of the first gear?

77% Answer Correctly

	1
	1.8
	2.2
	2

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 = \( \frac{N_1}{N_2} \) = \( \frac{32}{16} \) = 2