ASVAB Mechanical Comprehension Practice Test 32249 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.90
Score	0%	58%

Review

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

38% Answer Correctly

	output gear
	idler gear
	driven gear
	driver 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.

2 A = 5 ft., the green box weighs 20 lbs., and the blue box weighs 50 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	2 ft.
	8 ft.
	0.67 ft.
	6 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B

For this problem, the equation becomes:

20 lbs. x 5 ft. = 50 lbs. x d_B

d_B = \( \frac{20 \times 5 ft⋅lb}{50 lbs.} \) = \( \frac{100 ft⋅lb}{50 lbs.} \) = 2 ft.

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

	0
	2
	4
	1

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

4 If the force applied at the blue arrow over 9 ft. moves the green box 2.25 ft., what is the mechanical advantage of this lever?

56% Answer Correctly

	4.4
	4
	6
	-1

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 = \( \frac{9 ft.}{2.25 ft.} \) = 4

You might be wondering how having an effort distance of 4 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 4 times the resistance distance, the effort force must be \( \frac{1}{4} \) the resistance force. You're trading moving 4 times the distance for only having to use \( \frac{1}{4} \) the force.

An inclined plane increases ___________ to reduce ____________.

58% Answer Correctly

	force, power
	distance, force
	force, distance
	distance, power

Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.