ASVAB Mechanical Comprehension Practice Test 644458 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.03
Score	0%	61%

Review

1 If you have a gear train with three gears, the first with 26 teeth, the second with 18 teeth, and the third with 4 teeth, what is its mechanical advantage?

51% Answer Correctly

	3.3
	6.5
	2.2
	8.5

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 = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{26}{18} \) \( \frac{18}{4} \) = \( \frac{26}{4} \) = 6.5

Which of the following statements about drag is false?

58% Answer Correctly

	the amount of drag depends on the shape of an object
	slower objects experience more drag than faster objects
	the amount of drag depends on the speed of an object
	drag occurs during movement through a fluid

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.

3 A = 6 ft., the green box weighs 5 lbs., and the blue box weighs 10 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	30 ft.
	60 ft.
	3 ft.
	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:

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

d_B = \( \frac{5 \times 6 ft⋅lb}{10 lbs.} \) = \( \frac{30 ft⋅lb}{10 lbs.} \) = 3 ft.

A watt is the unit for which of the following?

71% Answer Correctly

	energy
	power
	mechanical advantage
	work

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.

Which of the following will increase the mechanical advantage of this inclined plane?

58% Answer Correctly

	increase the force acting at the blue arrow
	lengthen the ramp
	lower the force acting at the blue arrow
	shorten the ramp

Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In order to increase mechanical advantage, this ratio must increase which means making the effort distance longer and this can be accomplished by lengthening the length of the ramp.