Work, Energy and Power

Q. A 10 kg object is dropped from a height of 20 m. What is its speed just before it hits the ground? (Assume no air resistance)

A. 10 m/s
B. 14 m/s
C. 20 m/s
D. 28 m/s

Solution

Using conservation of energy: Potential Energy = Kinetic Energy. mgh = 0.5mv². v = sqrt(2gh) = sqrt(2 × 9.8 m/s² × 20 m) = 20 m/s.

Correct Answer: C — 20 m/s

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Q. A 3 kg object is moving with a velocity of 10 m/s. What is its momentum?

A. 15 kg·m/s
B. 30 kg·m/s
C. 10 kg·m/s
D. 5 kg·m/s

Solution

Momentum = mass × velocity = 3 kg × 10 m/s = 30 kg·m/s.

Correct Answer: B — 30 kg·m/s

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Q. A machine does 200 J of work in 10 seconds. What is its power output?

A. 20 W
B. 30 W
C. 40 W
D. 50 W

Solution

Power = Work / Time = 200 J / 10 s = 20 W.

Correct Answer: A — 20 W

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Q. A machine does 200 J of work in 5 seconds. What is its power output?

A. 20 W
B. 40 W
C. 50 W
D. 60 W

Solution

Power = Work / Time = 200 J / 5 s = 40 W.

Correct Answer: B — 40 W

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Q. An object with a mass of 4 kg is moving with a velocity of 3 m/s. What is its kinetic energy?

A. 6 J
B. 12 J
C. 24 J
D. 36 J

Solution

Kinetic Energy = 0.5 × m × v² = 0.5 × 4 kg × (3 m/s)² = 18 J.

Correct Answer: C — 24 J

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Q. How much work is done when a force of 25 N moves an object 8 m in the direction of the force?

A. 100 J
B. 150 J
C. 200 J
D. 250 J

Solution

Work = Force × Distance = 25 N × 8 m = 200 J.

Correct Answer: C — 200 J

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Q. How much work is done when a force of 50 N is applied to move an object 2 m horizontally?

A. 100 J
B. 50 J
C. 25 J
D. 200 J

Solution

Work = Force × Distance = 50 N × 2 m = 100 J.

Correct Answer: A — 100 J

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Q. If a 2 kg object is lifted to a height of 3 m, what is the gravitational potential energy gained?

A. 6 J
B. 12 J
C. 18 J
D. 24 J

Solution

Potential Energy = mgh = 2 kg × 9.8 m/s² × 3 m = 58.8 J.

Correct Answer: B — 12 J

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Q. If a car accelerates from rest to 20 m/s in 5 seconds, what is the average power output if the car has a mass of 1000 kg?

A. 4000 W
B. 8000 W
C. 16000 W
D. 20000 W

Solution

Work done = Change in Kinetic Energy = 0.5 × 1000 kg × (20 m/s)² = 200000 J. Power = Work / Time = 200000 J / 5 s = 40000 W.

Correct Answer: C — 16000 W

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Q. If a car accelerates from rest to a speed of 20 m/s in 10 seconds, what is the average power output if the car has a mass of 1000 kg?

A. 2000 W
B. 4000 W
C. 6000 W
D. 8000 W

Solution

Work done = Change in Kinetic Energy = 0.5 × 1000 kg × (20 m/s)² = 200000 J. Power = Work / Time = 200000 J / 10 s = 20000 W.

Correct Answer: C — 6000 W

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Q. If a force of 15 N is applied to move an object 4 m, how much work is done?

A. 30 J
B. 60 J
C. 75 J
D. 90 J

Solution

Work = Force × Distance = 15 N × 4 m = 60 J.

Correct Answer: D — 90 J

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Q. If a spring with a spring constant of 200 N/m is compressed by 0.5 m, what is the potential energy stored in the spring?

A. 25 J
B. 50 J
C. 100 J
D. 200 J

Solution

Potential Energy = 0.5 × k × x² = 0.5 × 200 N/m × (0.5 m)² = 25 J.

Correct Answer: B — 50 J

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Q. What is the kinetic energy of a 5 kg object moving at a speed of 4 m/s?

A. 10 J
B. 20 J
C. 40 J
D. 80 J

Solution

Kinetic Energy = 0.5 × m × v² = 0.5 × 5 kg × (4 m/s)² = 40 J.

Correct Answer: B — 20 J

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Q. What is the work done against gravity when lifting a 5 kg object to a height of 2 m?

A. 10 J
B. 20 J
C. 30 J
D. 40 J

Solution

Work = mgh = 5 kg × 9.8 m/s² × 2 m = 98 J.

Correct Answer: B — 20 J

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Q. What is the work done by a force of 15 N acting at an angle of 60 degrees to the direction of motion over a distance of 4 m?

A. 30 J
B. 60 J
C. 120 J
D. 15 J

Solution

Work = F × d × cos(θ) = 15 N × 4 m × cos(60°) = 15 N × 4 m × 0.5 = 30 J.

Correct Answer: B — 60 J

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Showing 1 to 15 of 15 (1 Pages)

Work, Energy and Power

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