ASVAB Mechanical Comprehension Practice Test 313361 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.89
Score	0%	58%

Review

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

	its mass
	its weight
	its direction
	its speed

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

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

37% Answer Correctly

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

3 What is the power output of a 6 hp engine that's 30% efficient?

40% Answer Correctly

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

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 6 hp x 550 \( \frac{ft⋅lb}{s} \) = 3300 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{30 \times 3300 \frac{ft⋅lb}{s}}{100} \) \( = \frac{99000 \frac{ft⋅lb}{s}}{100} \) = 990 \( \frac{ft⋅lb}{s} \)

4 What is the mechanical advantage of this inclined plane if the length of the ramp is 48 ft. and the height of the green box is 6 ft.?

82% Answer Correctly

	8
	7.2
	2
	12

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 = \( \frac{d_e}{d_r} \) = \( \frac{48 ft.}{6 ft.} \) = 8

One Horsepower (hp) is equal to how many watts?

76% Answer Correctly

	1
	1492
	746
	9.8

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.