ASVAB Mechanical Comprehension Practice Test 745739 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.22
Score	0%	64%

Review

1 If the handles of a wheelbarrow are 1.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 240 lbs. load concentrated at a point 0.5 ft. from the axle?

52% Answer Correctly

	23
	240
	158.6
	120

Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. In this problem we're looking for effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{240 \times 0.5}{1.0} \)
\( F_e = \frac{120.0}{1.0} \)
\( F_e = 120 \)

2 How much resistance could a 225 lb. effort force lift using a block and tackle pulley that has 8 ropes supporting the resistance?

81% Answer Correctly

	1792 lbs.
	1801.5 lbs.
	1803 lbs.
	1800 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 8. With a MA of 8, a 225 lbs. effort force could lift 225 lbs. x 8 = 1800 lbs. resistance.

What's the last gear in a gear train called?

38% Answer Correctly

	idler gear
	driven gear
	driver gear
	output gear

Solution

A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.

Tension is a force that does which of the following?

76% Answer Correctly

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

When all forces acting on a system cancel each other out, this is called:

80% Answer Correctly

	rest
	equilibrium
	potential energy
	stasis

Solution

When a system is stable or balanced (equilibrium) all forces acting on the system cancel each other out. In the case of torque, equilibrium means that the sum of the anticlockwise moments about a center of rotation equal the sum of the clockwise moments.