ASVAB Mechanical Comprehension Practice Test 996706 Results

Your Results Global Average
Questions 5 5
Correct 0 2.67
Score 0% 53%

Review

1

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

38% Answer Correctly

output gear

driver gear

idler gear

driven 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 What is the efficiency of a machine has work input of 90 ft⋅lb and work output of 67 ft⋅lb?
68% Answer Correctly
25%
1%
37%
75%
Solution
Due to friction, a machine will never be able to utilize 100% of its work input. A certain percentage of that input will be lost in overcoming friction within the machine. Effeciency is a measure of how much of a machine's work input can be turned into useful work output and is calculated by dividing work output by work input and multiplying the result by 100:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{67 ft⋅lb}{90 ft⋅lb} \times 100 \) \( = 75% \) %
3

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

45% Answer Correctly

kinetic energy

total mechanical energy

potential energy

acceleration
Solution

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

4 If A = 11 ft., B = 1 ft., C = 7 ft., the green box weighs 30 lbs. and the blue box weighs 50 lbs., what does the orange box have to weigh for this lever to balance?
44% Answer Correctly
160 lbs.
40 lbs.
30 lbs.
80 lbs.
Solution
In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB + fCdC

For this problem, this equation becomes:

30 lbs. x 11 ft. = 50 lbs. x 1 ft. + fC x 7 ft.

330 ft. lbs. = 50 ft. lbs. + fC x 7 ft.

fC = \( \frac{330 ft. lbs. - 50 ft. lbs.}{7 ft.} \) = \( \frac{280 ft. lbs.}{7 ft.} \) = 40 lbs.

5

Tension is a force that does which of the following?

76% Answer Correctly

heats up an object

slows an object

stretches 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.