ASVAB Mechanical Comprehension Practice Test 755899 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.16
Score	0%	63%

Review

The mechanical advantage of a wheel and axle is equal to the:

61% Answer Correctly

	difference in the diameters of the wheels
	ratio of the diameters of the wheels
	difference in the lengths of the axles
	length of the axle

Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

63% Answer Correctly

	pressure, volume
	pressure, density
	density, volume
	volume, mass

Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional".

3 If the green arrow in this diagram represents 1000 ft⋅lb of work, how far will the box move if it weighs 250 pounds?

72% Answer Correctly

	62 ft.
	4 ft.
	8 ft.
	1 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 1000 ft⋅lb and the resistance force is 250 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
1000 ft⋅lb = 250 lbs. x d_resistance
d_resistance = \( \frac{1000ft⋅lb}{250 lbs.} \) = 4 ft.

4 50 lbs. of effort is used by a machine to lift a 100 lbs. box. What is the mechanical advantage of the machine?

84% Answer Correctly

	3
	2
	1
	1.8

Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{100 lbs.}{50 lbs.} \) = 2

5 If the radius of the axle is 5 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?

36% Answer Correctly

	8
	1
	1
	0

Solution

The mechanical advantage of a wheel and axle lies in the difference in radius between the inner (axle) wheel and the outer wheel. But, this mechanical advantage is only realized when the input effort and load are applied to different wheels. Applying both input effort and load to the same wheel results in a mechanical advantage of 1.