ASVAB Mechanical Comprehension Practice Test 231864 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.27
Score	0%	65%

Review

Which of the following is not a characteristic of a ceramic?

61% Answer Correctly

	low density
	high melting point
	low corrosive action
	chemically stable

Solution

Ceramics are mixtures of metallic and nonmetallic elements that withstand exteme thermal, chemical, and pressure environments. They have a high melting point, low corrosive action, and are chemically stable. Examples include rock, sand, clay, glass, brick, and porcelain.

2 If you have a gear train with two gears, the first with 20 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
	2.8
	2.5
	1.3

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 = \( \frac{N_1}{N_2} \) = \( \frac{20}{16} \) = 1.3

3 A = 6 ft., the green box weighs 10 lbs., and the blue box weighs 25 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	2.4 ft.
	0.8 ft.
	0.6 ft.
	9.6 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B

For this problem, the equation becomes:

10 lbs. x 6 ft. = 25 lbs. x d_B

d_B = \( \frac{10 \times 6 ft⋅lb}{25 lbs.} \) = \( \frac{60 ft⋅lb}{25 lbs.} \) = 2.4 ft.

The mechanical advantage of a block and tackle is equal to which of the following?

69% Answer Correctly

	the number of pulleys
	the number of loads
	the number of connecting ropes
	the number of input forces

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

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

55% Answer Correctly

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

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.