ASVAB Mechanical Comprehension Practice Test 759376 Results

Your Results Global Average
Questions 5 5
Correct 0 3.28
Score 0% 66%

Review

1

Two or more pulleys used together are called:

71% Answer Correctly

gears

block and tackle

wheel and axle

third-class lever
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.

2

The science that deals with motion and the forces that produce motion is called which of the following?

57% Answer Correctly

engineering

physics

mechanics

aeronautics
Solution

Mechanics deals with motion and the forces that produce motion.

3

The mechanical advantage of connected gears is proportional to which characteristic of the gears?

73% Answer Correctly

speed

diameter

circumference

number of teeth
Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear.  For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

4

Power is the rate at which:

62% Answer Correctly

input force is transferred to output force

potential energy is converted into kinetic energy

work is done

friction is overcome
Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

5 What is the efficiency of a machine has work input of 95 ft⋅lb and work output of 23 ft⋅lb?
67% Answer Correctly
12%
100%
25%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{23 ft⋅lb}{95 ft⋅lb} \times 100 \) \( = 25% \) %