ASVAB Mechanical Comprehension Practice Test 474734 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.52
Score	0%	50%

Review

1 What is the power output of a 6 hp engine that's 35% efficient?

40% Answer Correctly

	0 \( \frac{ft⋅lb}{s} \)
	5 \( \frac{ft⋅lb}{s} \)
	4620 \( \frac{ft⋅lb}{s} \)
	1155 \( \frac{ft⋅lb}{s} \)

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 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{35 \times 3300 \frac{ft⋅lb}{s}}{100} \) \( = \frac{115500 \frac{ft⋅lb}{s}}{100} \) = 1155 \( \frac{ft⋅lb}{s} \)

2 A 360 lb. barrel is rolled up a 19 ft. ramp to a platform that's 4 ft. tall. What effort is required to move the barrel?

53% Answer Correctly

	68.2 lbs.
	75.8 lbs.
	83.4 lbs.
	151.6 lbs.

Solution

This problem describes an inclined plane and, for an inclined plane, 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 19 ft. = 360 lbs. x 4 ft.
F_e = \( \frac{1440 ft⋅lb}{19 ft.} \) = 75.8 lbs.

Specific gravity is a comparison of the density of an object with the density of:

57% Answer Correctly

	carbon
	air
	water
	oil

Solution

Specific gravity is the ratio of the density of equal volumes of a substance and water and is measured by a hyrdometer.

Which of the following will increase the mechanical advantage of a second-class lever?

55% Answer Correctly

	decrease the length of the lever
	move the object being lifted closer to the fulcrum
	move the fulcrum between the force and the object being lifted
	move the object being lifted farther away from the fulcrum

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.

Which of the following is not a modulus of elasticity?

47% Answer Correctly

	stress modulus
	bulk modulus
	stretch modulus
	shear modulus

Solution

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).