ASVAB Mechanical Comprehension Practice Test 523908 Results

Your Results Global Average
Questions 5 5
Correct 0 2.92
Score 0% 58%

Review

1

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

64% Answer Correctly

density, volume

pressure, volume

pressure, density

volume, mass
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".

2 How much work can a 3 hp engine do in 2 seconds?
53% Answer Correctly
12 ft⋅lb
3300 ft⋅lb
1 ft⋅lb
0 ft⋅lb
Solution
Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 3 hp \times 550 \frac{ft⋅lb}{s} \times 2s = 3300 ft⋅lb \)
3 What is the power output of a 2 hp engine that's 75% efficient?
40% Answer Correctly
412.5 \( \frac{ft⋅lb}{s} \)
1650 \( \frac{ft⋅lb}{s} \)
825 \( \frac{ft⋅lb}{s} \)
3300 \( \frac{ft⋅lb}{s} \)
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 2 hp x 550 \( \frac{ft⋅lb}{s} \) = 1100 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{75 \times 1100 \frac{ft⋅lb}{s}}{100} \) \( = \frac{82500 \frac{ft⋅lb}{s}}{100} \) = 825 \( \frac{ft⋅lb}{s} \)
4

Torque involves a perpendicular force applied to a lever arm that moves around a center of rotation. Increasing the length of the lever arm will do which of the following?

55% Answer Correctly

increase torque

decrease applied force

decrease torque

increase applied force
Solution

Torque measures force applied during rotation: τ = rF.  Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).

5 If you have a gear train with two gears, the first with 24 teeth and the second with 8 teeth, how many revolutions does the second gear make for each revolution of the first gear?
78% Answer Correctly
4
-2
3
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 = \( \frac{N_1}{N_2} \) = \( \frac{24}{8} \) = 3