ASVAB Mechanical Comprehension Practice Test 748186 Results

Your Results Global Average
Questions 5 5
Correct 0 2.74
Score 0% 55%

Review

1

Power is the rate at which:

62% Answer Correctly

friction is overcome

potential energy is converted into kinetic energy

work is done

input force is transferred to output force
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.

2 What is the power output of a 8 hp engine that's 30% efficient?
39% Answer Correctly
3960 \( \frac{ft⋅lb}{s} \)
2640 \( \frac{ft⋅lb}{s} \)
1320 \( \frac{ft⋅lb}{s} \)
5280 \( \frac{ft⋅lb}{s} \)
Solution
\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), Pi becomes 8 hp x 550 \( \frac{ft⋅lb}{s} \) = 4400 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{30 \times 4400 \frac{ft⋅lb}{s}}{100} \) \( = \frac{132000 \frac{ft⋅lb}{s}}{100} \) = 1320 \( \frac{ft⋅lb}{s} \)
3

What type of load is sudden and for a relatively short duration?

69% Answer Correctly

impact load

concentrated load

non-uniformly distributed load

dynamic load
Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

4

A screw is most like which of the following other simple machines?

50% Answer Correctly

wheel and axle

block and tackle

first-class lever

inclined plane
Solution

A screw is an inclined plane wrapped in ridges (threads) around a cylinder. The distance between these ridges defines the pitch of the screw and this distance is how far the screw advances when it is turned once. The mechanical advantage of a screw is its circumference divided by the pitch.

5 If the radius of the axle is 5 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?
52% Answer Correctly
5
0.63
3
1.6
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 8 and the output radius (where the resistance is being applied) is 5 for a mechanical advantage of \( \frac{8}{5} \) = 1.6