ASVAB Mechanical Comprehension Practice Test 200291 Results

Your Results Global Average
Questions 5 5
Correct 0 3.16
Score 0% 63%

Review

1 If you have a gear train with two gears, the first with 24 teeth and the second with 12 teeth, how many revolutions does the second gear make for each revolution of the first gear?
78% Answer Correctly
2
2.2
4
0.7
Solution

The gear ratio (Vr) of a gear train is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have only two gears so the equation becomes:

Vr = \( \frac{N_1}{N_2} \) = \( \frac{24}{12} \) = 2

2

Friction between two or more solid objects that are not moving relative to each other is called:

74% Answer Correctly

dynamic friction

static friction

gravitational friction

kinetic friction
Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.

3

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

45% Answer Correctly

kinetic energy

acceleration

total mechanical energy

potential energy
Solution

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

4 If the green arrow in this diagram represents 550 ft⋅lb of work, how far will the box move if it weighs 110 pounds?
73% Answer Correctly
5 ft.
27 ft.
440 ft.
55 ft.
Solution
The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

Win = Wout
Feffort x deffort = Fresistance x dresistance

In this problem, the effort work is 550 ft⋅lb and the resistance force is 110 lbs. and we need to calculate the resistance distance:

Win = Fresistance x dresistance
550 ft⋅lb = 110 lbs. x dresistance
dresistance = \( \frac{550ft⋅lb}{110 lbs.} \) = 5 ft.

5 If A = 12 ft., B = 1 ft., C = 11 ft., the green box weighs 25 lbs. and the blue box weighs 30 lbs., what does the orange box have to weigh for this lever to balance?
44% Answer Correctly
98.18 lbs.
6.14 lbs.
24.55 lbs.
12.27 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:

25 lbs. x 12 ft. = 30 lbs. x 1 ft. + fC x 11 ft.

300 ft. lbs. = 30 ft. lbs. + fC x 11 ft.

fC = \( \frac{300 ft. lbs. - 30 ft. lbs.}{11 ft.} \) = \( \frac{270 ft. lbs.}{11 ft.} \) = 24.55 lbs.