ASVAB Mechanical Comprehension Practice Test 367241 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.92
Score	0%	58%

Review

1 If input effort is 200 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 3?

79% Answer Correctly

	150ft⋅lb
	300ft⋅lb
	0ft⋅lb
	600 ft⋅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 200 ft⋅lb by 3 to produce an output effort of 600 ft⋅lb.

Which of the following statements about this pulley configuration is false?

48% Answer Correctly

	Changes the direction of and multiplies the effort force
	This is a block and tackle pulley configuration
	Only multiplies the effort force
	Mechanical advantage is the number of ropes that support the resistance

Solution

A block and tackle is a combination of one or more fixed pulleys and one or more movable pulleys where the fixed pulleys change the direction of the effort force and the movable pulleys multiply it. The mechanical advantage is equal to the number of times the effort force changes direction and can be increased by adding more pulley wheels to the system. An easy way to find the mechanical advantage of a block and tackle pulley system is to count the number of ropes that support the resistance.

The measure of how much of the power put into a machine is turned into movement or force is called:

56% Answer Correctly

	efficiency
	mechanical advantage
	force multiplication
	power

Solution

The efficiency of a machine describes how much of the power put into the machine is turned into movement or force. A 100% efficient machine would turn all of the input power into output movement or force. However, no machine is 100% efficient due to friction, heat, wear and other imperfections that consume input power without delivering any output.

4 A 270 lb. barrel is rolled up a 14 ft. ramp to a platform that's 2 ft. tall. What effort is required to move the barrel?

53% Answer Correctly

	40.6 lbs.
	41.6 lbs.
	43.6 lbs.
	38.6 lbs.

Solution

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

F_ed_e = F_rd_r

Plugging in the variables from this problem yields:

F_e x 14 ft. = 270 lbs. x 2 ft.
F_e = \( \frac{540 ft⋅lb}{14 ft.} \) = 38.6 lbs.

Which of the following is the formula for hydraulic pressure?

58% Answer Correctly

	P = FA²
	P = F/A
	P = FA
	P = F/A²

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).