ASVAB Mechanical Comprehension Practice Test 388025 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.73
Score	0%	55%

Review

1 If a 10 lbs. weight is placed 9 ft. from the fulcrum at the blue arrow and the green box is 8 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

61% Answer Correctly

	0 lbs.
	11.25 lbs.
	1 lbs.
	3.75 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 = \( \frac{R_bd_b}{d_a} \) = \( \frac{10 lbs. \times 9 ft.}{8 ft.} \) = \( \frac{90 ft⋅lb}{8 ft.} \) = 11.25 lbs.

2 A mass of air has a pressure of 9.0 psi and a volume of 45 ft.³. If the air is compressed to a new volume of 20 ft.³, what is the new pressure?

56% Answer Correctly

	30.4 psi
	20.3 psi
	40.5 psi
	10.1 psi

Solution

According to Boyle's Law, pressure and volume are inversely proportional:

\( \frac{P_1}{P_2} \) = \( \frac{V_2}{V_1} \)

In this problem, V₂ = 20 ft.³, V₁ = 45 ft.³ and P₁ = 9.0 psi. Solving for P₂:

P₂ = \( \frac{P_1}{\frac{V_2}{V_1}} \) = \( \frac{9.0 psi}{\frac{20 ft.^3}{45 ft.^3}} \) = 20.3 psi

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	first
	none of these, all levers offer mechanical advantage
	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.

A shovel is an example of which class of lever?

56% Answer Correctly

	a shovel is not a lever
	first
	third
	second

Solution

Torque involves a perpendicular force applied to a lever arm that moves around a center of rotation. Increasing the length of the lever arm will do which of the following?

54% Answer Correctly

	increase torque
	increase applied force
	decrease applied force
	decrease torque

Solution

Torque measures force applied during rotation: τ = rF. Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).