Work, Energy & Power: Essential Concepts for Exam Success

Work, Energy & Power

Q. A car accelerates from rest to a speed of 20 m/s. If its mass is 1000 kg, what is the kinetic energy of the car at this speed? (2000)

A. 200 J
B. 1000 J
C. 2000 J
D. 4000 J

Solution

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 1000 kg × (20 m/s)² = 0.5 × 1000 × 400 = 200000 J.

Correct Answer: C — 2000 J

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Q. A car accelerates from rest to a speed of 20 m/s. If the mass of the car is 1000 kg, what is the kinetic energy of the car at that speed? (2000)

A. 200 J
B. 1000 J
C. 2000 J
D. 4000 J

Solution

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 1000 kg × (20 m/s)² = 0.5 × 1000 × 400 = 200000 J.

Correct Answer: D — 4000 J

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Q. A car does 5000 J of work in moving a distance of 100 m. What is the average force exerted by the car? (2023)

A. 50 N
B. 100 N
C. 150 N
D. 200 N

Solution

Average Force = Work done / Distance = 5000 J / 100 m = 50 N

Correct Answer: A — 50 N

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Q. A car of mass 1000 kg accelerates from rest to a speed of 20 m/s. What is the kinetic energy gained?

A. 200,000 J
B. 100,000 J
C. 50,000 J
D. 20,000 J

Solution

Kinetic Energy = 0.5 * m * v² = 0.5 * 1000 kg * (20 m/s)² = 200,000 J.

Correct Answer: B — 100,000 J

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Q. A cyclist does 1500 J of work to climb a hill. If he takes 5 minutes, what is his average power output?

A. 5 W
B. 10 W
C. 15 W
D. 20 W

Solution

Power = Work / Time = 1500 J / (5 * 60 s) = 5 W.

Correct Answer: B — 10 W

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Q. A cyclist does 300 J of work to climb a hill. If the cyclist's mass is 75 kg, what is the height of the hill? (2023)

A. 0.4 m
B. 0.5 m
C. 0.6 m
D. 0.8 m

Solution

Potential Energy = mass × g × height; 300 J = 75 kg × 10 m/s² × height; height = 300 J / (75 kg × 10 m/s²) = 0.4 m

Correct Answer: B — 0.5 m

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Q. A cyclist does 300 J of work to climb a hill. If the height of the hill is 5 m, what is the mass of the cyclist? (g = 9.8 m/s²)

A. 6.12 kg
B. 10 kg
C. 15 kg
D. 20 kg

Solution

Using Work = mgh; m = Work / (gh) = 300 J / (9.8 m/s² * 5 m) = 6.12 kg.

Correct Answer: A — 6.12 kg

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Q. A cyclist does 300 J of work to climb a hill. If the hill is 5 m high, what is the effective weight of the cyclist? (2022)

A. 30 kg
B. 60 kg
C. 90 kg
D. 120 kg

Solution

Weight = Work done / height = 300 J / 5 m = 60 kg

Correct Answer: B — 60 kg

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Q. A cyclist does 300 J of work to climb a hill. If the hill is 5 m high, what is the weight of the cyclist? (2020)

A. 60 kg
B. 30 kg
C. 50 kg
D. 40 kg

Solution

Work = m × g × h. 300 J = m × 9.8 m/s² × 5 m. m = 300 J / (9.8 m/s² × 5 m) = 6.12 kg.

Correct Answer: A — 60 kg

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Q. A cyclist does 600 J of work to climb a hill. If he takes 30 seconds, what is his average power output? (2022)

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

Solution

Power = Work / Time = 600 J / 30 s = 20 W.

Correct Answer: B — 20 W

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Q. A cyclist is moving at a speed of 15 m/s. If the mass of the cyclist and the bicycle is 75 kg, what is the total kinetic energy?

A. 800 J
B. 900 J
C. 1000 J
D. 1200 J

Solution

KE = 0.5 × m × v² = 0.5 × 75 kg × (15 m/s)² = 0.5 × 75 × 225 = 8437.5 J.

Correct Answer: C — 1000 J

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Q. A cyclist is moving at a speed of 15 m/s. If the total mass of the cyclist and the bicycle is 75 kg, what is the kinetic energy?

A. 843.75 J
B. 562.5 J
C. 1687.5 J
D. 1125 J

Solution

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 75 kg × (15 m/s)² = 0.5 × 75 × 225 = 8437.5 J.

Correct Answer: A — 843.75 J

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Q. A cyclist is moving up a hill and gains 3000 J of potential energy. If the mass of the cyclist and the bicycle is 75 kg, what is the height of the hill? (g = 9.8 m/s²)

A. 4.08 m
B. 3.06 m
C. 2.04 m
D. 1.5 m

Solution

Height (h) = PE / (mg) = 3000 J / (75 kg * 9.8 m/s²) = 4.08 m.

Correct Answer: A — 4.08 m

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Q. A force of 10 N is applied to move a box 5 m across a floor. What is the work done on the box?

A. 10 J
B. 20 J
C. 50 J
D. 5 J

Solution

Work done = Force × Distance = 10 N × 5 m = 50 J

Correct Answer: B — 20 J

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Q. A force of 10 N is applied to move a box 5 m across a floor. What is the work done by the force?

A. 10 J
B. 20 J
C. 50 J
D. 5 J

Solution

Work done = Force × Distance = 10 N × 5 m = 50 J

Correct Answer: B — 20 J

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Q. A force of 10 N is applied to move a box 5 m along a horizontal surface. What is the work done by the force? (2021)

A. 20 J
B. 50 J
C. 10 J
D. 5 J

Solution

Work done = Force × Distance = 10 N × 5 m = 50 J

Correct Answer: B — 50 J

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Q. A force of 10 N is applied to move an object 5 m in the direction of the force. What is the work done by the force?

A. 10 J
B. 20 J
C. 50 J
D. 5 J

Solution

Work done (W) = Force (F) × Distance (d) × cos(θ). Here, θ = 0° (force and displacement are in the same direction). W = 10 N × 5 m × cos(0°) = 10 N × 5 m = 50 J.

Correct Answer: B — 20 J

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Q. A force of 20 N is applied at an angle of 60° to the horizontal while moving an object 4 m. What is the work done?

A. 40 J
B. 80 J
C. 20 J
D. 60 J

Solution

Work done (W) = F × d × cos(θ) = 20 N × 4 m × cos(60°) = 20 × 4 × 0.5 = 40 J.

Correct Answer: B — 80 J

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Q. A force of 50 N is applied to move an object 4 m. How much work is done?

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

Solution

Work = Force * Distance = 50 N * 4 m = 200 J.

Correct Answer: C — 200 J

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Q. A machine does 1200 J of work in 60 seconds. What is its efficiency if the input energy is 2000 J? (2022)

A. 60%
B. 70%
C. 80%
D. 90%

Solution

Efficiency = (Output Work / Input Energy) * 100 = (1200 J / 2000 J) * 100 = 60%.

Correct Answer: A — 60%

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Q. A machine does 1500 J of work in 30 seconds. What is its power output?

A. 50 W
B. 30 W
C. 75 W
D. 100 W

Solution

Power (P) = Work (W) / Time (t). P = 1500 J / 30 s = 50 W.

Correct Answer: A — 50 W

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Q. A person lifts a 10 kg box to a height of 2 m. What is the work done against gravity? (g = 9.8 m/s²)

A. 196 J
B. 98 J
C. 20 J
D. 10 J

Solution

Work = mgh = 10 kg * 9.8 m/s² * 2 m = 196 J.

Correct Answer: A — 196 J

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Q. A spring is compressed by 0.2 m and has a spring constant of 300 N/m. What is the potential energy stored in the spring?

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

Solution

Potential Energy in spring (PE) = 0.5 × k × x² = 0.5 × 300 N/m × (0.2 m)² = 0.5 × 300 × 0.04 = 6 J.

Correct Answer: B — 12 J

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Q. A spring is compressed by 0.5 m and has a spring constant of 200 N/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 (PE) = 0.5 * k * x² = 0.5 * 200 N/m * (0.5 m)² = 25 J.

Correct Answer: A — 25 J

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Q. An object is lifted to a height of 10 m. If the mass of the object is 5 kg, what is the gravitational potential energy gained? (g = 9.8 m/s²)

A. 49 J
B. 98 J
C. 245 J
D. 490 J

Solution

Potential Energy (PE) = mgh = 5 kg * 9.8 m/s² * 10 m = 490 J.

Correct Answer: B — 98 J

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Q. An object is lifted vertically 10 m. If the mass of the object is 5 kg, what is the gravitational potential energy gained?

A. 50 J
B. 100 J
C. 150 J
D. 200 J

Solution

Potential Energy (PE) = mgh = 5 kg * 9.8 m/s² * 10 m = 490 J.

Correct Answer: B — 100 J

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Q. An object is lifted vertically 4 m against gravity. If the mass of the object is 10 kg, what is the work done against gravity? (g = 9.8 m/s²)

A. 39.2 J
B. 78.4 J
C. 98 J
D. 196 J

Solution

Work done (W) = mgh = 10 kg × 9.8 m/s² × 4 m = 392 J.

Correct Answer: B — 78.4 J

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Q. An object is lifted vertically 4 m against gravity. If the mass of the object is 3 kg, what is the work done against gravity? (g = 9.8 m/s²)

A. 117.6 J
B. 29.4 J
C. 39.2 J
D. 78.4 J

Solution

Work done (W) = mgh = 3 kg × 9.8 m/s² × 4 m = 117.6 J.

Correct Answer: A — 117.6 J

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Q. An object is lifted vertically 4 m. If the weight of the object is 50 N, how much work is done against gravity?

A. 100 J
B. 200 J
C. 150 J
D. 50 J

Solution

Work done (W) = Force (F) × Distance (d) = 50 N × 4 m = 200 J.

Correct Answer: B — 200 J

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Q. An object is moving with a speed of 15 m/s and has a mass of 3 kg. What is its kinetic energy?

A. 67.5 J
B. 45 J
C. 90 J
D. 135 J

Solution

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 3 kg × (15 m/s)² = 0.5 × 3 × 225 = 337.5 J.

Correct Answer: C — 90 J

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Showing 31 to 60 of 103 (4 Pages)

Work, Energy & Power

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