ASVAB Mechanical Comprehension Practice Test 580801 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.57
Score	0%	51%

Review

1 If the radius of the axle is 3 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?

36% Answer Correctly

	-5
	2
	8
	1

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.

Which of the following is not a characteristic of a ceramic?

61% Answer Correctly

	high melting point
	chemically stable
	low corrosive action
	low density

Solution

Ceramics are mixtures of metallic and nonmetallic elements that withstand exteme thermal, chemical, and pressure environments. They have a high melting point, low corrosive action, and are chemically stable. Examples include rock, sand, clay, glass, brick, and porcelain.

3 If you have a gear train with three gears, the first with 28 teeth, the second with 16 teeth, and the third with 8 teeth, what is its mechanical advantage?

51% Answer Correctly

	0.5
	3.5
	1.2
	10.5

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 = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{28}{16} \) \( \frac{16}{8} \) = \( \frac{28}{8} \) = 3.5

What type of load creates different stresses at different locations on a structure?

60% Answer Correctly

	impact load
	dynamic load
	static uniformly distributed load
	non-uniformly distributed load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

5 If this lever is in equilibrium with an effort force of 8.33 ft. lb. at the blue arrow and a resistance force of 5 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	0.54
	0.66
	1.8
	0.6

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{5 ft.}{8.33 ft.} \) = 0.6

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.6 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.