ASVAB Mechanical Comprehension Practice Test 432995 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.20
Score	0%	64%

Review

1 A = 7 ft., the green box weighs 15 lbs., and the blue box weighs 60 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	420 ft.
	3.5 ft.
	1.75 ft.
	5.25 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. 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

For this problem, the equation becomes:

15 lbs. x 7 ft. = 60 lbs. x d_B

d_B = \( \frac{15 \times 7 ft⋅lb}{60 lbs.} \) = \( \frac{105 ft⋅lb}{60 lbs.} \) = 1.75 ft.

Which of the following statements about drag is false?

58% Answer Correctly

	the amount of drag depends on the speed of an object
	the amount of drag depends on the shape of an object
	slower objects experience more drag than faster objects
	drag occurs during movement through a fluid

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.

A shovel is an example of which class of lever?

56% Answer Correctly

	second
	first
	third
	a shovel is not a lever

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.

4 If a 75 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow and the green box is 6 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

61% Answer Correctly

	37.5 lbs.
	112.5 lbs.
	25 lbs.
	75 lbs.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for R_a, our missing value, and plugging in our variables yields:

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{75 lbs. \times 3 ft.}{6 ft.} \) = \( \frac{225 ft⋅lb}{6 ft.} \) = 37.5 lbs.

The force amplification achieved by using a tool, mechanical device or machine system is called:

80% Answer Correctly

	power
	work
	mechanical advantage
	efficiency

Solution

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Such a device utilizes input force and trades off forces against movement to amplify and/or change its direction.