ASVAB Mechanical Comprehension Practice Test 955453 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.83
Score	0%	57%

Review

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 fulcrum between the force and the object being lifted
	move the object being lifted closer to the fulcrum
	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.

2 If A = 11 ft., B = 2 ft., C = 6 ft., the green box weighs 50 lbs. and the blue box weighs 55 lbs., what does the orange box have to weigh for this lever to balance?

44% Answer Correctly

	220 lbs.
	73.33 lbs.
	550 lbs.
	146.67 lbs.

Solution

In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B + f_Cd_C

For this problem, this equation becomes:

50 lbs. x 11 ft. = 55 lbs. x 2 ft. + f_C x 6 ft.

550 ft. lbs. = 110 ft. lbs. + f_C x 6 ft.

f_C = \( \frac{550 ft. lbs. - 110 ft. lbs.}{6 ft.} \) = \( \frac{440 ft. lbs.}{6 ft.} \) = 73.33 lbs.

Concurrent forces:

55% Answer Correctly

	act along the same line of action
	act in a common dimension
	act in a common plane
	pass through a common point

Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

A watt is the unit for which of the following?

71% Answer Correctly

	power
	work
	energy
	mechanical advantage

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.

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

57% Answer Correctly

	carbon
	air
	oil
	water

Solution

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