ASVAB Mechanical Comprehension Practice Test 878892 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.14
Score	0%	63%

Review

Which of the following is not a type of simple machine?

58% Answer Correctly

	lever
	gear
	screw
	pulley

Solution

The six types of simple machines are the lever, wheel and axle, pulley, inclined plane, wedge, and screw.

2 If you have a gear train with three gears, the first with 28 teeth, the second with 10 teeth, and the third with 4 teeth, what is its mechanical advantage?

51% Answer Correctly

	7
	8.5
	14
	10

Solution

The mechanical advantage of a gear train is its gear ratio. The gear ratio (V_r) 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 three gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{28}{10} \) \( \frac{10}{4} \) = \( \frac{28}{4} \) = 7

3 If the green arrow in this diagram represents 240 ft⋅lb of work, how far will the box move if it weighs 60 pounds?

72% Answer Correctly

	1 ft.
	16 ft.
	4 ft.
	30 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 240 ft⋅lb and the resistance force is 60 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
240 ft⋅lb = 60 lbs. x d_resistance
d_resistance = \( \frac{240ft⋅lb}{60 lbs.} \) = 4 ft.

Two or more pulleys used together are called:

71% Answer Correctly

	gears
	third-class lever
	wheel and axle
	block and tackle

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.

Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?

64% Answer Correctly

	do 100 ft. lb. of work in 4 minutes 12 seconds
	do the work in 3 minutes
	do the work in 2 minutes
	do 25 ft. lb. of work in 2 minutes 5 seconds

Solution

Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.