ASVAB Mechanical Comprehension Practice Test 935639 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.04
Score	0%	61%

Review

Friction between two or more solid objects that are not moving relative to each other is called:

73% Answer Correctly

	kinetic friction
	dynamic friction
	static friction
	gravitational friction

Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.

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

61% Answer Correctly

	low corrosive action
	high melting point
	chemically stable
	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 What is the mechanical advantage of this inclined plane if the length of the ramp is 8 ft. and the height of the green box is 2 ft.?

82% Answer Correctly

	5.5
	4
	7
	3.6

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 = \( \frac{d_e}{d_r} \) = \( \frac{8 ft.}{2 ft.} \) = 4

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	none of these, all levers offer mechanical advantage
	third
	first
	second

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.

5 What is the power output of a 7 hp engine that's 40% efficient?

40% Answer Correctly

	1540 \( \frac{ft⋅lb}{s} \)
	770 \( \frac{ft⋅lb}{s} \)
	513.3 \( \frac{ft⋅lb}{s} \)
	6160 \( \frac{ft⋅lb}{s} \)

Solution

\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), P_i becomes 7 hp x 550 \( \frac{ft⋅lb}{s} \) = 3850 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{40 \times 3850 \frac{ft⋅lb}{s}}{100} \) \( = \frac{154000 \frac{ft⋅lb}{s}}{100} \) = 1540 \( \frac{ft⋅lb}{s} \)