ASVAB Mechanical Comprehension Practice Test 880127 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.24
Score	0%	65%

Review

Which of the following will increase the mechanical advantage of a second-class lever?

55% Answer Correctly

	move the object being lifted closer to the fulcrum
	move the fulcrum between the force and the object being lifted
	decrease the length of the lever
	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.

Which of the following is the formula for hydraulic pressure?

58% Answer Correctly

	P = F/A
	P = FA²
	P = F/A²
	P = FA

Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).

3 How much resistance could a 105 lb. effort force lift using a block and tackle pulley that has 6 ropes supporting the resistance?

81% Answer Correctly

	632 lbs.
	567 lbs.
	630 lbs.
	210 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 6. With a MA of 6, a 105 lbs. effort force could lift 105 lbs. x 6 = 630 lbs. resistance.

4 If input effort is 900 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 3?

79% Answer Correctly

	5400ft⋅lb
	2700 ft⋅lb
	675ft⋅lb
	10800ft⋅lb

Solution

Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 3 will multiply an input effort of 900 ft⋅lb by 3 to produce an output effort of 2700 ft⋅lb.

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

	decrease torque
	increase applied force
	increase torque
	decrease applied force

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).