ASVAB Mechanical Comprehension Practice Test 507999 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.40
Score	0%	68%

Review

1 If A = 7 ft. and the green box weighs 5 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	140 ft⋅lb
	35 ft⋅lb
	1 ft⋅lb
	17 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 5 ft. x 7 lbs. = 35 ft⋅lb

Tension is a force that does which of the following?

75% Answer Correctly

	compacts an object
	stretches an object
	heats up an object
	slows an object

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.

3 If the green arrow in this diagram represents 630 ft⋅lb of work, how far will the box move if it weighs 210 pounds?

72% Answer Correctly

	420 ft.
	6 ft.
	3 ft.
	105 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 630 ft⋅lb and the resistance force is 210 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
630 ft⋅lb = 210 lbs. x d_resistance
d_resistance = \( \frac{630ft⋅lb}{210 lbs.} \) = 3 ft.

A shovel is an example of which class of lever?

56% Answer Correctly

	a shovel is not a lever
	first
	third
	second

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.

5 If the green box weighs 15 lbs. and is 3 ft. from the fulcrum, how far from the fulcrum would a 25 lbs. weight need to be placed to balance the lever?

61% Answer Correctly

	1.8 ft.
	3.6 ft.
	5.4 ft.
	45 ft.

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 d_b, our missing value, and plugging in our variables yields:

d_b = \( \frac{R_ad_a}{R_b} \) = \( \frac{15 lbs. \times 3 ft.}{25 lbs.} \) = \( \frac{45 ft⋅lb}{25 lbs.} \) = 1.8 ft.