ASVAB Mechanical Comprehension Practice Test 898974 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.76
Score	0%	55%

Review

1 What is the power output of a 7 hp engine that's 85% efficient?

40% Answer Correctly

	6545 \( \frac{ft⋅lb}{s} \)
	595 \( \frac{ft⋅lb}{s} \)
	3272.5 \( \frac{ft⋅lb}{s} \)
	1090.8 \( \frac{ft⋅lb}{s} \)

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 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{85 \times 3850 \frac{ft⋅lb}{s}}{100} \) \( = \frac{327250 \frac{ft⋅lb}{s}}{100} \) = 3272.5 \( \frac{ft⋅lb}{s} \)

A fixed pulley has a mechanical advantage of:

68% Answer Correctly

	1
	2
	-1
	0

Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

Which of the following statements about this pulley configuration is false?

48% Answer Correctly

	Changes the direction of and multiplies the effort force
	Mechanical advantage is the number of ropes that support the resistance
	This is a block and tackle pulley configuration
	Only multiplies the effort force

Solution

A block and tackle is a combination of one or more fixed pulleys and one or more movable pulleys where the fixed pulleys change the direction of the effort force and the movable pulleys multiply it. The mechanical advantage is equal to the number of times the effort force changes direction and can be increased by adding more pulley wheels to the system. An easy way to find the mechanical advantage of a block and tackle pulley system is to count the number of ropes that support the resistance.

Which of the following will increase the mechanical advantage of this inclined plane?

59% Answer Correctly

	shorten the ramp
	lower the force acting at the blue arrow
	increase the force acting at the blue arrow
	lengthen the ramp

Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In order to increase mechanical advantage, this ratio must increase which means making the effort distance longer and this can be accomplished by lengthening the length of the ramp.

What is work?

60% Answer Correctly

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