Work, Energy & Power: Essential Concepts for Exam Success

Work, Energy & Power

Q. A 10 kg object is dropped from a height of 20 m. What is its potential energy at the top? (g = 9.8 m/s²) (1960)

A. 196 J
B. 98 J
C. 294 J
D. 490 J

Solution

Potential Energy (PE) = mgh = 10 kg × 9.8 m/s² × 20 m = 1960 J.

Correct Answer: C — 294 J

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Q. A 10 kg object is dropped from a height of 20 m. What is its potential energy at the top? (2020)

A. 200 J
B. 1000 J
C. 1500 J
D. 3000 J

Solution

Potential Energy = mass × g × height = 10 kg × 10 m/s² × 20 m = 2000 J

Correct Answer: B — 1000 J

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Q. A 10 kg object is dropped from a height of 20 m. What is the potential energy at the top? (2022)

A. 200 J
B. 1000 J
C. 500 J
D. 400 J

Solution

Potential Energy = mass × g × height = 10 kg × 9.8 m/s² × 20 m = 1960 J

Correct Answer: B — 1000 J

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Q. A 10 kg object is lifted 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. 39.2 J

Solution

Work done (W) = m × g × h = 10 kg × 9.8 m/s² × 2 m = 196 J.

Correct Answer: A — 196 J

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Q. A 10 kg object is moving with a velocity of 4 m/s. What is its kinetic energy?

A. 80 J
B. 40 J
C. 20 J
D. 160 J

Solution

Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 10 kg × (4 m/s)² = 80 J

Correct Answer: A — 80 J

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Q. A 10 kg object is thrown upwards with a velocity of 15 m/s. What is the maximum height it reaches? (g = 9.8 m/s²)

A. 11.5 m
B. 22.5 m
C. 15.0 m
D. 7.5 m

Solution

Using energy conservation: KE_initial = PE_max; 0.5 * m * v² = mgh; h = v² / (2g) = (15 m/s)² / (2 * 9.8 m/s²) = 11.5 m.

Correct Answer: A — 11.5 m

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Q. A 10 N force is applied at an angle of 60° to the horizontal while moving an object 4 m. What is the work done?

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

Solution

Work done (W) = F × d × cos(θ) = 10 N × 4 m × cos(60°) = 10 × 4 × 0.5 = 20 J.

Correct Answer: C — 30 J

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Q. A 10 N force is applied to move an object 3 m. What is the work done if the force is applied at an angle of 60 degrees to the direction of motion?

A. 15 J
B. 30 J
C. 25 J
D. 20 J

Solution

Work done = Force × Distance × cos(θ) = 10 N × 3 m × cos(60°) = 10 N × 3 m × 0.5 = 15 J

Correct Answer: A — 15 J

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Q. A 1000 kg car is moving at a speed of 15 m/s. What is its kinetic energy?

A. 112,500 J
B. 75,000 J
C. 50,000 J
D. 25,000 J

Solution

Kinetic Energy = 0.5 * m * v² = 0.5 * 1000 kg * (15 m/s)² = 112,500 J.

Correct Answer: A — 112,500 J

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Q. A 1000 kg car is moving at a speed of 36 km/h. What is its kinetic energy? (1 km/h = 1/3.6 m/s) (2000)

A. 500 J
B. 1000 J
C. 2000 J
D. 5000 J

Solution

First convert speed: 36 km/h = 10 m/s. KE = 0.5 × m × v² = 0.5 × 1000 kg × (10 m/s)² = 0.5 × 1000 × 100 = 50000 J.

Correct Answer: C — 2000 J

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Q. A 1000 W electric motor runs for 2 hours. How much work does it do? (2023)

A. 720,000 J
B. 1,000,000 J
C. 2,000,000 J
D. 1,440,000 J

Solution

Work = Power × Time = 1000 W × (2 × 3600 s) = 7,200,000 J.

Correct Answer: D — 1,440,000 J

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Q. A 15 kg object is lifted to a height of 4 m. What is the work done against gravity? (g = 9.8 m/s²) (2021)

A. 588 J
B. 5880 J
C. 392 J
D. 294 J

Solution

Work = mgh = 15 kg * 9.8 m/s² * 4 m = 588 J.

Correct Answer: A — 588 J

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Q. A 15 kg object is moving at a speed of 4 m/s. What is its kinetic energy?

A. 120 J
B. 240 J
C. 480 J
D. 60 J

Solution

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 15 kg × (4 m/s)² = 0.5 × 15 × 16 = 120 J.

Correct Answer: B — 240 J

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Q. A 1500 kg car accelerates from rest to a speed of 25 m/s. What is the work done on the car?

A. 468,750 J
B. 375,000 J
C. 250,000 J
D. 187,500 J

Solution

Work done = Change in Kinetic Energy = 0.5 * m * v² = 0.5 * 1500 kg * (25 m/s)² = 468,750 J.

Correct Answer: A — 468,750 J

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Q. A 1500 kg car is moving at a speed of 25 m/s. What is its kinetic energy? (2021)

A. 468,750 J
B. 1,875,000 J
C. 937,500 J
D. 750,000 J

Solution

Kinetic Energy = 0.5 × mass × velocity² = 0.5 × 1500 kg × (25 m/s)² = 468,750 J

Correct Answer: B — 1,875,000 J

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Q. A 2 kg object is lifted to a height of 5 m. What is the potential energy gained by the object? (2022)

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

Solution

Potential Energy = mass × g × height = 2 kg × 10 m/s² × 5 m = 100 J

Correct Answer: B — 20 J

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Q. A 2 kg object is lifted to a height of 5 m. What is the potential energy gained by the object? (g = 9.8 m/s²)

A. 98 J
B. 19.6 J
C. 39.2 J
D. 49 J

Solution

Potential Energy = mass × g × height = 2 kg × 9.8 m/s² × 5 m = 98 J

Correct Answer: A — 98 J

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Q. A 2 kg object is pushed with a force of 10 N over a distance of 5 m. What is the work done on the object?

A. 25 J
B. 50 J
C. 75 J
D. 100 J

Solution

Work done = Force * Distance = 10 N * 5 m = 50 J.

Correct Answer: B — 50 J

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Q. A 3 kg object is dropped from a height of 10 m. What is its potential energy at the top? (g = 9.8 m/s²)

A. 294 J
B. 30 J
C. 39.2 J
D. 19.6 J

Solution

Potential Energy (PE) = m × g × h = 3 kg × 9.8 m/s² × 10 m = 294 J.

Correct Answer: A — 294 J

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Q. A 3 kg object is dropped from a height of 10 m. What is the potential energy at the top? (2022)

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

Solution

Potential Energy = mass × g × height = 3 kg × 10 m/s² × 10 m = 300 J

Correct Answer: C — 90 J

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Q. A 3 kg object is dropped from a height of 5 m. What is the potential energy at the top? (g = 9.8 m/s²)

A. 14.7 J
B. 29.4 J
C. 39.2 J
D. 49.05 J

Solution

PE = mgh = 3 kg × 9.8 m/s² × 5 m = 147 J.

Correct Answer: C — 39.2 J

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Q. A 3 kg object is lifted to a height of 4 m. 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. A 3 kg object is pushed with a force of 12 N over a distance of 4 m. What is the work done on the object?

A. 24 J
B. 36 J
C. 48 J
D. 60 J

Solution

Work done (W) = Force (F) × Distance (d) = 12 N × 4 m = 48 J.

Correct Answer: C — 48 J

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Q. A 4 kg object is lifted to a height of 2 m. What is the work done against gravity? (2022)

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

Solution

Work done = mass × g × height = 4 kg × 10 m/s² × 2 m = 80 J

Correct Answer: B — 80 J

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Q. A 4 kg object is lifted to a height of 5 m. What is the work done against gravity? (g = 9.8 m/s²)

A. 19.6 J
B. 39.2 J
C. 49 J
D. 196 J

Solution

Work done against gravity = mgh = 4 kg × 9.8 m/s² × 5 m = 196 J.

Correct Answer: B — 39.2 J

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Q. A 5 kg object is dropped from a height of 10 m. What is its potential energy at the top? (g = 9.8 m/s²)

A. 490 J
B. 98 J
C. 50 J
D. 100 J

Solution

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

Correct Answer: A — 490 J

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Q. A 5 kg object is dropped from a height of 10 m. What is its speed just before it hits the ground? (g = 9.8 m/s²)

A. 14 m/s
B. 20 m/s
C. 10 m/s
D. 15 m/s

Solution

Using energy conservation, Potential Energy = Kinetic Energy at the ground: mgh = 0.5mv²; v = √(2gh) = √(2 × 9.8 m/s² × 10 m) = 14 m/s

Correct Answer: A — 14 m/s

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Q. A 50 kg object is moving with a velocity of 4 m/s. What is its kinetic energy?

A. 100 J
B. 200 J
C. 400 J
D. 800 J

Solution

Kinetic Energy (KE) = 0.5 * m * v² = 0.5 * 50 kg * (4 m/s)² = 400 J.

Correct Answer: C — 400 J

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Q. A block of mass 2 kg is lifted to a height of 5 m. What is the work done against gravity? (g = 9.8 m/s²)

A. 98 J
B. 196 J
C. 49 J
D. 20 J

Solution

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

Correct Answer: B — 196 J

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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 that speed?

A. 200,000 J
B. 100,000 J
C. 50,000 J
D. 400,000 J

Solution

Kinetic Energy (KE) = 0.5 × m × v² = 0.5 × 1000 kg × (20 m/s)² = 0.5 × 1000 × 400 = 200,000 J.

Correct Answer: B — 100,000 J

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Showing 1 to 30 of 103 (4 Pages)

Work, Energy & Power

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