ASVAB Mechanical Comprehension Practice Test 988613 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.44
Score	0%	69%

Review

The measure of how much of the power put into a machine is turned into movement or force is called:

56% Answer Correctly

	efficiency
	power
	mechanical advantage
	force multiplication

Solution

The efficiency of a machine describes how much of the power put into the machine is turned into movement or force. A 100% efficient machine would turn all of the input power into output movement or force. However, no machine is 100% efficient due to friction, heat, wear and other imperfections that consume input power without delivering any output.

2 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

	5
	3.5
	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 = \( \frac{N_1}{N_2} \) = \( \frac{24}{12} \) = 2

3 What's the mechanical advantage of a wedge that's 2 inches wide and 16 inches long?

83% Answer Correctly

	8.8
	13
	2
	8

Solution

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{16 in.}{2 in.} \) = 8

Which of the following will increase the mechanical advantage of a second-class lever?

55% Answer Correctly

	move the fulcrum between the force and the object being lifted
	decrease the length of the lever
	move the object being lifted farther away from the fulcrum
	move the object being lifted closer to the fulcrum

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.

5 If A = 4 ft. and the green box weighs 15 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	240 ft⋅lb
	20 ft⋅lb
	120 ft⋅lb
	60 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 15 ft. x 4 lbs. = 60 ft⋅lb