ASVAB Mechanical Comprehension Practice Test 530845 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.40
Score	0%	68%

Review

The standard unit of energy is the:

73% Answer Correctly

	Joule
	Horsepower
	Volt
	Watt

Solution

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).

2 How much work can a 8 hp engine do in 7 seconds?

52% Answer Correctly

	16 ft⋅lb
	2 ft⋅lb
	32 ft⋅lb
	30800 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:
\( W = 8 hp \times 550 \frac{ft⋅lb}{s} \times 7s = 30800 ft⋅lb \)

3 If you have a gear train with two gears, the first with 40 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

	3.3
	1.1
	6.3
	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 = \( \frac{N_1}{N_2} \) = \( \frac{40}{12} \) = 3.3

4 What is the mechanical advantage of this inclined plane if the length of the ramp is 24 ft. and the height of the green box is 4 ft.?

82% Answer Correctly

	8
	6
	12
	7.5

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 = \( \frac{d_e}{d_r} \) = \( \frac{24 ft.}{4 ft.} \) = 6

A shovel is an example of which class of lever?

56% Answer Correctly

	second
	a shovel is not a lever
	first
	third

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.