ASVAB Mechanical Comprehension Practice Test 930116 Results

Your Results Global Average
Questions 5 5
Correct 0 2.96
Score 0% 59%

Review

1 If you have a gear train with three gears, the first with 24 teeth, the second with 16 teeth, and the third with 8 teeth, what is its mechanical advantage?
50% Answer Correctly
3.3
3
-3
9

Solution

The mechanical advantage of a gear train is its gear ratio. The gear ratio (Vr) 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 three gears so the equation becomes:

Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{24}{16} \) \( \frac{16}{8} \) = \( \frac{24}{8} \) = 3


2

The science that deals with motion and the forces that produce motion is called which of the following?

57% Answer Correctly

aeronautics

physics

engineering

mechanics


Solution

Mechanics deals with motion and the forces that produce motion.


3 The green box weighs 55 lbs. and a 45 lbs. weight is placed 7 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?
57% Answer Correctly
22.91 ft.
1.43 ft.
17.18 ft.
5.73 ft.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for da, our missing value, and plugging in our variables yields:

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{45 lbs. \times 7 ft.}{55 lbs.} \) = \( \frac{315 ft⋅lb}{55 lbs.} \) = 5.73 ft.


4

For a hydraulic system, pressure applied to the input of the system will increase the pressure in which parts of the system?

58% Answer Correctly

the portions of the system at an altitude above the input

all of these are correct

everywhere in the system

the portions of the system at an altitude below the input


Solution

Pascal's law states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. For a hydraulic system, this means that a pressure applied to the input of the system will increase the pressure everywhere in the system.


5

The force exerted on an object due to gravity is called:

70% Answer Correctly

mass

density

weight

potential energy


Solution

Mass is an intrinsic property of matter and does not vary. Weight is the force exerted on the mass of an object due to gravity and a specific case of Newton's Second Law of Motion. Replace force with weight and acceleration with acceleration due to gravity on Earth (g) and the result is the formula for weight: W = mg or, substituting for g, weight equals mass multiplied by 9.8 m/s2.