ASVAB Mechanical Comprehension Practice Test 596721 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.74
Score	0%	55%

Review

Power is the rate at which:

62% Answer Correctly

	input force is transferred to output force
	work is done
	friction is overcome
	potential energy is converted into kinetic energy

Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

2 If A = 7 ft. and the green box weighs 5 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	35 ft⋅lb
	70 ft⋅lb
	0 ft⋅lb
	8 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 5 ft. x 7 lbs. = 35 ft⋅lb

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

59% Answer Correctly

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

4 What is the power output of a 5 hp engine that's 25% efficient?

40% Answer Correctly

	343.8 \( \frac{ft⋅lb}{s} \)
	125 \( \frac{ft⋅lb}{s} \)
	687.5 \( \frac{ft⋅lb}{s} \)
	5 \( \frac{ft⋅lb}{s} \)

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 5 hp x 550 \( \frac{ft⋅lb}{s} \) = 2750 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{25 \times 2750 \frac{ft⋅lb}{s}}{100} \) \( = \frac{68750 \frac{ft⋅lb}{s}}{100} \) = 687.5 \( \frac{ft⋅lb}{s} \)

The advantage of using a third-class lever is that it increases:

37% Answer Correctly

	the force applied to the load
	the distance traveled by the load
	the mechanical advantage of the lever
	the speed of the load

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.