ASVAB Mechanical Comprehension Practice Test 769028 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.68
Score	0%	54%

Review

1 If the force applied at the blue arrow over 5 ft. moves the green box 1.67 ft., what is the mechanical advantage of this lever?

56% Answer Correctly

	4.5
	3
	3.3
	9

Solution

Mechanical advantage (MA) can be calculated knowing only the distance the effort (blue arrow) moves and the distance the resistance (green box) moves. The equation is:

MA = \( \frac{E_d}{R_d} \)

where E_d is the effort distance and R_d is the resistance distance. For this problem, the equation becomes:

MA = \( \frac{5 ft.}{1.67 ft.} \) = 3

You might be wondering how having an effort distance of 3 times the resistance distance is an advantage. Remember the principle of moments. For a lever in equilibrium the effort torque equals the resistance torque. Because torque is force x distance, if the effort distance is 3 times the resistance distance, the effort force must be \( \frac{1}{3} \) the resistance force. You're trading moving 3 times the distance for only having to use \( \frac{1}{3} \) the force.

The mass of an object correlates to the size of the object but ultimately depends on:

66% Answer Correctly

	the object's potential energy
	the object's weight
	the object's density
	gravity

Solution

Mass is a measure of the amount of matter in an object. In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

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

38% Answer Correctly

	driven gear
	output gear
	driver gear
	idler 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.

A fixed pulley is useful for which of the following?

53% Answer Correctly

	multiplying the input distance
	multiplying the input force
	changing the direction of the output force
	changing the direction of the input force

Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

Which class of lever is used to increase force on an object in the same direction as the force is applied?

53% Answer Correctly

	first
	second
	third
	all of these

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.