ASVAB Mechanical Comprehension Practice Test 63269 Results

Your Results Global Average
Questions 5 5
Correct 0 2.89
Score 0% 58%

Review

1

One Horsepower (hp) is equal to how many watts?

76% Answer Correctly

1

1492

746

9.8
Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

2

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

its weight

its mass

its speed

its direction
Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

3 If the green box weighs 50 lbs. and is 7 ft. from the fulcrum, how far from the fulcrum would a 25 lbs. force need to be applied to balance the lever?
58% Answer Correctly
4.67 ft.
14 ft.
3.5 ft.
0 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 db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{50 lbs. \times 7 ft.}{25 lbs.} \) = \( \frac{350 ft⋅lb}{25 lbs.} \) = 14 ft.

4

Which of the following is the formula for gravitational potential energy?

61% Answer Correctly

\(PE = { 1 \over 2} mv^2\)

\(PE = mg^2h\)

\(PE = { 1 \over 2} mg^2\)

\(PE = mgh\)
Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s2).

5 What is the power output of a 6 hp engine that's 50% efficient?
40% Answer Correctly
300 \( \frac{ft⋅lb}{s} \)
825 \( \frac{ft⋅lb}{s} \)
1650 \( \frac{ft⋅lb}{s} \)
8 \( \frac{ft⋅lb}{s} \)
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 6 hp x 550 \( \frac{ft⋅lb}{s} \) = 3300 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{50 \times 3300 \frac{ft⋅lb}{s}}{100} \) \( = \frac{165000 \frac{ft⋅lb}{s}}{100} \) = 1650 \( \frac{ft⋅lb}{s} \)