ASVAB Mechanical Comprehension Practice Test 462706 Results

Your Results Global Average
Questions 5 5
Correct 0 2.88
Score 0% 58%

Review

1

Boyle's law defines the relationship between pressure and volume as:

58% Answer Correctly

\(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

\(\frac{P_1}{P_2} = {V_1}{V_2}\)

\({P_1}{P_2} = {V_1}{V_2}\)

\(\frac{P_1}{P_2} = \frac{V_1}{V_2}\)
Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional". Expressed as a formula, that's \(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

2

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

61% Answer Correctly

Pascal's law

conservation of mechanical energy

mechanical advantage

work-energy theorem
Solution

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.

3 If the green box weighs 55 lbs. and is 1 ft. from the fulcrum, how far from the fulcrum would a 75 lbs. weight need to be placed to balance the lever?
61% Answer Correctly
55 ft.
0.73 ft.
0 ft.
0.24 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 = \( \frac{R_ad_a}{R_b} \) = \( \frac{55 lbs. \times 1 ft.}{75 lbs.} \) = \( \frac{55 ft⋅lb}{75 lbs.} \) = 0.73 ft.

4

A fixed pulley has a mechanical advantage of:

68% Answer Correctly

0

-1

2

1
Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

5 What is the power output of a 9 hp engine that's 25% efficient?
40% Answer Correctly
1237.5 \( \frac{ft⋅lb}{s} \)
2475 \( \frac{ft⋅lb}{s} \)
3712.5 \( \frac{ft⋅lb}{s} \)
0 \( \frac{ft⋅lb}{s} \)
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 9 hp x 550 \( \frac{ft⋅lb}{s} \) = 4950 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{25 \times 4950 \frac{ft⋅lb}{s}}{100} \) \( = \frac{123750 \frac{ft⋅lb}{s}}{100} \) = 1237.5 \( \frac{ft⋅lb}{s} \)