ASVAB Mechanical Comprehension Practice Test 273406 Results

Your Results Global Average
Questions 5 5
Correct 0 3.07
Score 0% 61%

Review

1 If the radius of the axle is 7 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?
41% Answer Correctly
7
0.88
1.14
8
Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 7 and the output radius (where the resistance is being applied) is 8 for a mechanical advantage of \( \frac{7}{8} \) = 0.88

2

A watt is the unit for which of the following?

71% Answer Correctly

mechanical advantage

energy

work

power
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.

3 What is the efficiency of a machine has work input of 205 ft⋅lb and work output of 82 ft⋅lb?
67% Answer Correctly
20%
40%
80%
0%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{82 ft⋅lb}{205 ft⋅lb} \times 100 \) \( = 40% \) %
4

Hydraulics is the transmission of force through the use of which of the following?

73% Answer Correctly

torque

air pressure

liquids

gear systems
Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).

5

For any given surface, the coefficient of static friction is ___________ the coefficient of kinetic friction.

54% Answer Correctly

lower than

opposite

higher than

equal to
Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).