ASVAB Mechanical Comprehension Practice Test 219896 Results

Your Results Global Average
Questions 5 5
Correct 0 3.13
Score 0% 63%

Review

1 If the green box weighs 65 lbs. and 60 lbs. of force is applied 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?
55% Answer Correctly
6.46 ft.
9 ft.
455 ft.
3.23 ft.

Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{60 lbs. \times 7 ft.}{65 lbs.} \) = \( \frac{420 ft⋅lb}{65 lbs.} \) = 6.46 ft.


2 If you have a gear train with two gears, the first with 24 teeth and the second with 16 teeth, how many revolutions does the second gear make for each revolution of the first gear?
77% Answer Correctly
-6.5
1.4
0.8
1.5

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 = \( \frac{N_1}{N_2} \) = \( \frac{24}{16} \) = 1.5


3 If the green box weighs 55 lbs. and is 1 ft. from the fulcrum, how far from the fulcrum would a 20 lbs. weight need to be placed to balance the lever?
61% Answer Correctly
0.69 ft.
2.75 ft.
11 ft.
55 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 db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{55 lbs. \times 1 ft.}{20 lbs.} \) = \( \frac{55 ft⋅lb}{20 lbs.} \) = 2.75 ft.


4

When it comes to force, mass and acceleration have what kind of relationship?

66% Answer Correctly

logarithmic

inverse

exponential

linear


Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.


5

The principle of moments defines equilibrium in terms of:

53% Answer Correctly

power

energy

speed

torque


Solution

According to the principle of moments, you can maintain equilibrium if the moments (forces) tending to clockwise rotation are equal to the moments tending to counterclockwise rotation. Another name for these moments of force is torque.