ASVAB Mechanical Comprehension Practice Test 6776 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.73
Score	0%	55%

Review

1 What is the power output of a 3 hp engine that's 65% efficient?

40% Answer Correctly

	2145 \( \frac{ft⋅lb}{s} \)
	1072.5 \( \frac{ft⋅lb}{s} \)
	3217.5 \( \frac{ft⋅lb}{s} \)
	195 \( \frac{ft⋅lb}{s} \)

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 3 hp x 550 \( \frac{ft⋅lb}{s} \) = 1650 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{65 \times 1650 \frac{ft⋅lb}{s}}{100} \) \( = \frac{107250 \frac{ft⋅lb}{s}}{100} \) = 1072.5 \( \frac{ft⋅lb}{s} \)

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

64% Answer Correctly

	density, volume
	pressure, density
	pressure, volume
	volume, mass

Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional".

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

	45 lbs
	0.83 lbs
	90 lbs
	810 lbs

Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. Plugging in the variables from this problem yields:

F_e x 3 ft. = 270 lbs x 0.5 ft
F_e = 135 ft-lb. / 3 ft
F_e= 45 lbs

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
	lengthen the ramp
	increase the force acting at the blue arrow

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.

A truck is using a rope to pull a car. Tension in the rope is greatest in which of the following places?

50% Answer Correctly

	in the middle
	near the car
	near the truck
	tension is equal in all parts of the rope

Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.