ASVAB Mechanical Comprehension Practice Test 578736 Results

Your Results Global Average
Questions 5 5
Correct 0 2.86
Score 0% 57%

Review

1

Which of the following represents the force a surface exerts when an object presses against it?

48% Answer Correctly

normal force

friction

mass

counter force
Solution

Normal force (FN) represents the force a surface exerts when an object presses against it.

2

Which of the following represents how much two materials resist sliding across each other?

53% Answer Correctly

normal friction

static friction

coefficient of friction

kinetic friction
Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other.  Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

3

A watt is the unit for which of the following?

71% Answer Correctly

power

work

energy

mechanical advantage
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.

4

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

third-class lever

first-class lever

inclined plane

second-class lever
Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

5 If A = 10 ft., B = 2 ft., C = 7 ft., the green box weighs 30 lbs. and the blue box weighs 40 lbs., what does the orange box have to weigh for this lever to balance?
44% Answer Correctly
15.71 lbs.
3 lbs.
31.43 lbs.
60 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. = 40 lbs. x 2 ft. + fC x 7 ft.

300 ft. lbs. = 80 ft. lbs. + fC x 7 ft.

fC = \( \frac{300 ft. lbs. - 80 ft. lbs.}{7 ft.} \) = \( \frac{220 ft. lbs.}{7 ft.} \) = 31.43 lbs.