ASVAB Mechanical Comprehension Practice Test 894950 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.27
Score	0%	65%

Review

The force required to initally get an object moving is __________ the force required to keep it moving.

76% Answer Correctly

	opposite
	higher than
	lower than
	the same as

Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).

2 What is the power output of a 2 hp engine that's 90% efficient?

40% Answer Correctly

	990 \( \frac{ft⋅lb}{s} \)
	247.5 \( \frac{ft⋅lb}{s} \)
	3960 \( \frac{ft⋅lb}{s} \)
	330 \( \frac{ft⋅lb}{s} \)

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 2 hp x 550 \( \frac{ft⋅lb}{s} \) = 1100 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{90 \times 1100 \frac{ft⋅lb}{s}}{100} \) \( = \frac{99000 \frac{ft⋅lb}{s}}{100} \) = 990 \( \frac{ft⋅lb}{s} \)

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

61% Answer Correctly

	low density
	high melting point
	low corrosive action
	chemically stable

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.

4 If the green arrow in this diagram represents 180 ft⋅lb of work, how far will the box move if it weighs 60 pounds?

73% Answer Correctly

	1 ft.
	3 ft.
	20 ft.
	240 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 180 ft⋅lb and the resistance force is 60 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
180 ft⋅lb = 60 lbs. x d_resistance
d_resistance = \( \frac{180ft⋅lb}{60 lbs.} \) = 3 ft.

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

74% Answer Correctly

	kinetic friction
	gravitational friction
	static friction
	dynamic 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.