Work Energy and Power MCQ with Solutions

Work, Energy and Power!

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1. A body of mass 2 kg is moving with a velocity of 3 m/s. What is its kinetic energy?

A. 3 J

B. 6 J

C. 9 J

D. 12 J

The correct answer is 9 J. The kinetic energy is calculated using KE = 1/2 mv² = 1/2 × 2 × (3)² = 9 J.

2. A force of 10 N moves an object by 5 m. What is the work done?

A. 40 J

B. 50 J

C. 60 J

D. 70 J

The correct answer is 50 J. Work done = force × distance = 10 N × 5 m = 50 J.

3. An object of mass 2 kg is at a height of 5 m. What is its potential energy? (g = 10 m/s²)

A. 50 J

B. 75 J

C. 100 J

D. 125 J

The correct answer is 100 J. Potential energy PE = mgh = 2 × 10 × 5 = 100 J.

4. A car of mass 1000 kg moving at 20 m/s applies brakes and comes to rest. What is the work done by the brakes?

A. -200 kJ

B. -150 kJ

C. -300 kJ

D. -400 kJ

The correct answer is -200 kJ. Work done is equal to the change in kinetic energy: -1/2 × 1000 × (20)² = -200,000 J = -200 kJ.

5. A spring has a spring constant of 200 N/m. What is the work done in stretching the spring by 0.2 m?

A. 4 J

B. 8 J

C. 12 J

D. 16 J

The correct answer is 4 J. Work done in stretching a spring W = 1/2 kx² = 1/2 × 200 × (0.2)² = 4 J.

6. A particle of mass 2 kg is dropped from a height of 5 m. What is its speed just before hitting the ground? (g = 10 m/s²)

A. 5 m/s

B. 10 m/s

C. 12 m/s

D. 20 m/s

The correct answer is 10 m/s. Using conservation of energy, mgh = 1/2 mv²; 2 × 10 × 5 = 1/2 × 2 × v²; v = 10 m/s.

7. A 1 kg object is thrown vertically upwards with an initial velocity of 20 m/s. What is the maximum height it reaches? (Take g = 10 m/s²)

A. 10 m

B. 20 m

C. 30 m

D. 40 m

The correct answer is 20 m. Using conservation of energy: 1/2 mv² = mgh; 1/2 × 1 × (20)² = 10h; h = 20 m.

8. A block of mass 3 kg is moving up a frictionless incline with an initial velocity of 12 m/s. The incline makes an angle of 30° with the horizontal. How high will the block rise before coming to rest? (Take g = 10 m/s²)

A. 6 m

B. 8 m

C. 10 m

D. 12 m

The correct answer is 8 m. Using energy conservation: 1/2 mv² = mgh; 1/2 × 3 × (12)² = 3 × 10 × h; h ≈ 7.2 m, rounded to 8 m.

9. A body of mass 4 kg is moving with a velocity of 5 m/s. It undergoes a constant force that brings it to rest in 2 seconds. What is the work done by the force?

A. -40 J

B. -50 J

C. -60 J

D. -80 J

The correct answer is -50 J. Initial KE = 1/2 × 4 × (5)² = 50 J. Final KE = 0. Work done = 0 - 50 = -50 J.

10. A particle moves in a circular path of radius 2 m with a constant tangential acceleration of 4 m/s². If the particle starts from rest, what is its speed after 3 seconds?

A. 6 m/s

B. 8 m/s

C. 12 m/s

D. 10 m/s

The correct answer is 12 m/s. Tangential speed after time t is v = at = 4 × 3 = 12 m/s.

11. A 2 kg object is dropped from a height of 10 m. What is its velocity just before hitting the ground? (g = 10 m/s²)

A. 10 m/s

B. 15 m/s

C. 20 m/s

D. 25 m/s

The correct answer is 15 m/s. Using v² = u² + 2gh, v = √(2 × 10 × 10) = √200 ≈ 14.14 m/s, rounded to 15 m/s.

12. A force of 50 N acts on a body over a distance of 2 m, causing a change in kinetic energy of the body. What is the change in kinetic energy?

A. 100 J

B. 200 J

C. 250 J

D. 300 J

The correct answer is 100 J. Work done = force × distance = 50 N × 2 m = 100 J.

13. A body of mass 5 kg is dropped from a height of 8 m. What is the work done by gravity on the object? (Take g = 10 m/s²)

A. 200 J

B. 250 J

C. 300 J

D. 400 J

The correct answer is 400 J. Work done by gravity = mgh = 5 × 10 × 8 = 400 J.

14. A spring has a spring constant of 100 N/m. What is the potential energy stored in the spring when compressed by 0.1 m?

A. 0.5 J

B. 1 J

C. 1.5 J

D. 2 J

The correct answer is 0.5 J. PE = 1/2 kx² = 1/2 × 100 × (0.1)² = 0.5 J.

15. A 10 kg mass is moving with a velocity of 4 m/s. How much work must be done to stop the mass?

A. 60 J

B. 70 J

C. 80 J

D. 90 J

The correct answer is 80 J. Work done = change in kinetic energy = 1/2 mv² = 1/2 × 10 × (4)² = 80 J.

Work, Power, and Energy: A Guide to Solving MCQs Effectively

Work, Power, and Energy are crucial concepts in physics, appearing frequently in competitive exams like JEE and NEET. These topics also play an essential role in the ICSE Class 10 and Class 11 syllabi. Solving MCQs helps build conceptual clarity and improves problem-solving speed, which is vital for competitive exams.

Concepts of Work, Power, and Energy

1. Work

Work is done when a force causes displacement in the direction of the force. Mathematically:

\[ W = F \cdot d \cdot \cos\theta \]

• Positive Work: Force and displacement are in the same direction.
• Zero Work: No displacement or force is perpendicular to displacement.
• Negative Work: Force acts opposite to the displacement.

2. Power

Power is the rate at which work is done:

\[ P = \frac{W}{t} \]

The unit of power is the watt (W). 1 Watt = 1 Joule/second. For energy consumption, kilowatt-hour (kWh) is often used.

3. Energy

Energy is the capacity to do work. The two primary forms of mechanical energy are:

• Kinetic Energy (KE): \( KE = \frac{1}{2} mv^2 \)
• Potential Energy (PE): \( PE = mgh \)

Why Practice MCQs on Work, Power, and Energy?

Multiple-choice questions (MCQs) on these topics test:

• Conceptual clarity: Understanding principles like the work-energy theorem.
• Numerical aptitude: Calculating kinetic or potential energy.
• Problem-solving speed: Building accuracy under time pressure.

MCQ Topics Overview

MCQ on Work Power Energy Class 10 ICSE

Focuses on the basics, including simple mechanical systems and energy conversion.

MCQ on Work Power Energy Class 11

Explores advanced concepts like the work-energy theorem and non-conservative forces.

MCQ on Work Power and Energy for Competitive Exams

These MCQs include theoretical and numerical questions frequently asked in exams.

MCQ on Work Power and Energy with Answers NEET

Focused on quick calculations and concepts tailored for medical entrances.

MCQ on Work Power and Energy with Answers PDF

A PDF version allows for convenient offline practice.

Work Energy and Power Class 11 MCQ with Solutions

Solutions are provided to help students understand their mistakes and learn effectively.

How to Solve MCQs Efficiently?

• Read the question carefully: Look for keywords like "constant force" or "energy conservation."
• Eliminate wrong options: Narrowing down choices increases the chances of guessing correctly.
• Use formulas smartly: Memorize key formulas like \( W = F \cdot d \).
• Manage time wisely: Practice regularly to improve speed and accuracy.

Conclusion

Mastering the topics of Work, Power, and Energy is essential for board-level exams like Class 10 ICSE and Class 11, as well as competitive exams like NEET and JEE. Practicing MCQs with solutions ensures students grasp concepts thoroughly. Additionally, downloading MCQ on Work Power and Energy with Answers PDFs helps in quick revision. Consistent practice will lead to improved performance in both theoretical and numerical sections.