ASVAB Mechanical Comprehension Practice Test 962566 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.95
Score	0%	59%

Review

Which of the following is not a type of structural load?

49% Answer Correctly

	occupancy load
	live load
	wind load
	dead load

Solution

Dead load is the weight of the building and materials, live load is additional weight due to occupancy or use, snow load is the weight of accumulated snow on a structure and wind load is the force of wind pressures against structure surfaces.

2 If A = 12 ft., B = 1 ft., C = 7 ft., the green box weighs 35 lbs. and the blue box weighs 55 lbs., what does the orange box have to weigh for this lever to balance?

43% Answer Correctly

	420 lbs.
	0 lbs.
	52.14 lbs.
	156.43 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:

35 lbs. x 12 ft. = 55 lbs. x 1 ft. + f_C x 7 ft.

420 ft. lbs. = 55 ft. lbs. + f_C x 7 ft.

f_C = \( \frac{420 ft. lbs. - 55 ft. lbs.}{7 ft.} \) = \( \frac{365 ft. lbs.}{7 ft.} \) = 52.14 lbs.

Normal force is generally equal to the __________ of an object.

61% Answer Correctly

	coefficient of friction
	mass
	weight
	density

Solution

Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.

Gear ratio indicates which of the following about two connected gears?

59% Answer Correctly

	work done
	power conversion
	efficiency
	mechanical advantage

Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear. For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

5 How much resistance could a 35 lb. effort force lift using a block and tackle pulley that has 4 ropes supporting the resistance?

81% Answer Correctly

	142 lbs.
	140 lbs.
	70 lbs.
	143 lbs.

Solution

The mechanical advantage (MA) of a block and tackle pulley is equal to the number of times the effort force changes direction. An easy way to count how many times the effort force changes direction is to count the number of ropes that support the resistance which, in this problem, is 4. With a MA of 4, a 35 lbs. effort force could lift 35 lbs. x 4 = 140 lbs. resistance.