ASVAB Mechanical Comprehension Practice Test 576570 Results

Your Results Global Average
Questions 5 5
Correct 0 2.94
Score 0% 59%

Review

1

What is the first step to solving a problem where multiple forces are acting on an object?

61% Answer Correctly

calculate kinetic energy

calculate the total force

calculate the net force

calculate potential energy
Solution

In mechanics, multiple forces are often acting on a particular object and, taken together, produce the net force acting on that object. Like force, net force is a vector quantity in that it has magnitude and direction.

2

The principle of moments defines equilibrium in terms of:

53% Answer Correctly

torque

energy

power

speed
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.

3

Tension is a force that does which of the following?

75% Answer Correctly

heats up an object

slows an object

compacts an object

stretches an object
Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.

4 If the green box weighs 5 lbs. and is 7 ft. from the fulcrum, how much weight would need to be placed at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 2 ft.?
63% Answer Correctly
5.83 lbs.
17.5 lbs.
52.5 lbs.
10 lbs.
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 Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{5 lbs. \times 7 ft.}{2 ft.} \) = \( \frac{35 ft⋅lb}{2 ft.} \) = 17.5 lbs.

5 What is the power output of a 8 hp engine that's 40% efficient?
39% Answer Correctly
586.7 \( \frac{ft⋅lb}{s} \)
1760 \( \frac{ft⋅lb}{s} \)
0 \( \frac{ft⋅lb}{s} \)
320 \( \frac{ft⋅lb}{s} \)
Solution
\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), Pi becomes 8 hp x 550 \( \frac{ft⋅lb}{s} \) = 4400 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{40 \times 4400 \frac{ft⋅lb}{s}}{100} \) \( = \frac{176000 \frac{ft⋅lb}{s}}{100} \) = 1760 \( \frac{ft⋅lb}{s} \)