ASVAB Mechanical Comprehension Practice Test 38111 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.29
Score	0%	66%

Review

1 If you have a gear train with two gears, the first with 28 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

	1.8
	3.5
	3.3
	3.8

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 = \( \frac{N_1}{N_2} \) = \( \frac{28}{16} \) = 1.8

Gear ratio indicates which of the following about two connected gears?

59% Answer Correctly

	power conversion
	efficiency
	work done
	mechanical advantage

Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear. For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

The mass of an object correlates to the size of the object but ultimately depends on:

66% Answer Correctly

	the object's density
	the object's weight
	the object's potential energy
	gravity

Solution

Mass is a measure of the amount of matter in an object. In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

4 How much work can a 2 hp engine do in 9 seconds?

52% Answer Correctly

	1 ft⋅lb
	9900 ft⋅lb
	8 ft⋅lb
	0 ft⋅lb

Solution

Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 2 hp \times 550 \frac{ft⋅lb}{s} \times 9s = 9900 ft⋅lb \)

One Horsepower (hp) is equal to how many watts?

76% Answer Correctly

	9.8
	1
	1492
	746

Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.