ASVAB Mechanical Comprehension Practice Test 246754 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.05
Score	0%	61%

Review

1 If the green arrow in this diagram represents 800 ft⋅lb of work, how far will the box move if it weighs 160 pounds?

72% Answer Correctly

	5 ft.
	0 ft.
	80 ft.
	640 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 800 ft⋅lb and the resistance force is 160 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
800 ft⋅lb = 160 lbs. x d_resistance
d_resistance = \( \frac{800ft⋅lb}{160 lbs.} \) = 5 ft.

2 How much work can a 3 hp engine do in 7 seconds?

52% Answer Correctly

	11550 ft⋅lb
	12 ft⋅lb
	0 ft⋅lb
	1 ft⋅lb

Solution

Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 3 hp \times 550 \frac{ft⋅lb}{s} \times 7s = 11550 ft⋅lb \)

3 If the green box weighs 25 lbs. and is 3 ft. from the fulcrum, how far from the fulcrum would a 10 lbs. weight need to be placed to balance the lever?

61% Answer Correctly

	22.5 ft.
	1.88 ft.
	75 ft.
	7.5 ft.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for d_b, our missing value, and plugging in our variables yields:

d_b = \( \frac{R_ad_a}{R_b} \) = \( \frac{25 lbs. \times 3 ft.}{10 lbs.} \) = \( \frac{75 ft⋅lb}{10 lbs.} \) = 7.5 ft.

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

61% Answer Correctly

	low density
	low corrosive action
	chemically stable
	high melting point

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.

What is work?

60% Answer Correctly

	The potential for exertion
	Force per unit time
	The movement of an object by a force
	Force per unit distance

Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.