ASVAB Mechanical Comprehension Practice Test 197532 Results

Your Results Global Average
Questions 5 5
Correct 0 2.82
Score 0% 56%

Review

1

Concurrent forces:

55% Answer Correctly

pass through a common point

act in a common plane

act in a common dimension

act along the same line of action
Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

2 A = 7 ft., the green box weighs 40 lbs., and the blue box weighs 50 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
0 ft.
5.6 ft.
11.2 ft.
22.4 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:

fAdA = fBdB

For this problem, the equation becomes:

40 lbs. x 7 ft. = 50 lbs. x dB

dB = \( \frac{40 \times 7 ft⋅lb}{50 lbs.} \) = \( \frac{280 ft⋅lb}{50 lbs.} \) = 5.6 ft.

3 If the radius of the axle is 3 and the radius of the wheel is 4, what is the mechanical advantage of this wheel and axle configuration?
52% Answer Correctly
-1
1.33
1
0.75
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 4 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{4}{3} \) = 1.33

4

Power is the rate at which:

63% Answer Correctly

work is done

potential energy is converted into kinetic energy

friction is overcome

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.

5 If A = 10 ft., B = 2 ft., C = 6 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
60 lbs.
3 lbs.
16.67 lbs.
33.33 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 10 ft. = 50 lbs. x 2 ft. + fC x 6 ft.

300 ft. lbs. = 100 ft. lbs. + fC x 6 ft.

fC = \( \frac{300 ft. lbs. - 100 ft. lbs.}{6 ft.} \) = \( \frac{200 ft. lbs.}{6 ft.} \) = 33.33 lbs.