Mechanics - Work, Energy & Power for Competitive Exams

Mechanics - Work, Energy & Power

Q. A 1 kg ball is thrown upwards with a speed of 20 m/s. What is the maximum height it reaches? (g = 10 m/s²) (2021)

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

Solution

Maximum Height (h) = v^2 / (2g) = (20 m/s)^2 / (2 * 10 m/s²) = 20 m

Correct Answer: A — 20 m

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Q. A 1 kg object is moving with a velocity of 4 m/s. What is its kinetic energy? (2021)

A. 8 J
B. 4 J
C. 16 J
D. 2 J

Solution

Kinetic Energy (KE) = 1/2 * m * v^2 = 1/2 * 1 kg * (4 m/s)^2 = 8 J.

Correct Answer: A — 8 J

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Q. A 10 kg block slides down a frictionless incline of height 5 m. What is its speed at the bottom? (2020)

A. 5 m/s
B. 10 m/s
C. 15 m/s
D. 20 m/s

Solution

Using conservation of energy, PE at top = KE at bottom. mgh = 1/2 mv^2. 10 kg * 9.8 m/s^2 * 5 m = 1/2 * 10 kg * v^2. Solving gives v = 10 m/s.

Correct Answer: B — 10 m/s

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Q. A 10 kg block slides down a frictionless incline of height 5 m. What is its speed at the bottom? (g = 10 m/s²) (2020)

A. 10 m/s
B. 5 m/s
C. 15 m/s
D. 20 m/s

Solution

Using conservation of energy, PE at top = KE at bottom: mgh = 1/2 mv²; v = sqrt(2gh) = sqrt(2 * 10 m/s² * 5 m) = 10 m/s

Correct Answer: A — 10 m/s

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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? (g = 10 m/s²) (2022)

A. 200 J
B. 100 J
C. 50 J
D. 300 J

Solution

Potential Energy (PE) = m * g * h = 10 kg * 10 m/s² * 20 m = 2000 J

Correct Answer: A — 200 J

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Q. A 10 kg object is dropped from a height of 20 m. What is its speed just before it hits the ground? (g = 10 m/s²) (2022)

A. 20 m/s
B. 10 m/s
C. 15 m/s
D. 5 m/s

Solution

Using the formula v = √(2gh) = √(2 * 10 m/s² * 20 m) = √400 = 20 m/s.

Correct Answer: A — 20 m/s

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Q. A 10 kg object is dropped from a height of 5 m. What is its potential energy at the top? (2021)

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

Solution

Potential Energy (PE) = m * g * h = 10 kg * 9.8 m/s^2 * 5 m = 490 J.

Correct Answer: B — 100 J

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Q. A 10 kg object is moving with a velocity of 4 m/s. What is its total mechanical energy if it is at a height of 5 m? (2020)

A. 120 J
B. 140 J
C. 100 J
D. 80 J

Solution

Total Mechanical Energy = Kinetic Energy + Potential Energy = (1/2 * 10 kg * (4 m/s)²) + (10 kg * 9.8 m/s² * 5 m) = 80 J + 490 J = 570 J

Correct Answer: B — 140 J

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Q. A 2 kg ball is dropped from a height of 10 m. What is its speed just before it hits the ground? (2022)

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

Solution

Using energy conservation, v = sqrt(2gh) = sqrt(2 * 9.8 m/s² * 10 m) = 14 m/s.

Correct Answer: A — 14 m/s

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Q. A 2 kg ball is dropped from a height of 10 m. What is its speed just before it hits the ground? (g = 10 m/s²) (2023)

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

Solution

Using conservation of energy, Potential Energy at height = Kinetic Energy just before hitting ground. mgh = 1/2 mv^2. Solving gives v = sqrt(2gh) = sqrt(2 * 10 m/s² * 10 m) = 14.14 m/s.

Correct Answer: A — 10 m/s

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Q. A 2 kg ball is dropped from a height of 20 m. What is its speed just before it hits the ground? (g = 10 m/s²) (2023)

A. 10 m/s
B. 20 m/s
C. 15 m/s
D. 5 m/s

Solution

Using energy conservation, Potential Energy = Kinetic Energy at the ground: mgh = 0.5 mv^2; v = sqrt(2gh) = sqrt(2 * 10 m/s² * 20 m) = 20 m/s

Correct Answer: B — 20 m/s

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Q. A 2 kg block slides down a frictionless incline of height 3 m. What is its speed at the bottom? (2023)

A. 6 m/s
B. 3 m/s
C. 4 m/s
D. 5 m/s

Solution

Using conservation of energy, Potential Energy at top = Kinetic Energy at bottom: mgh = 1/2 mv^2; v = sqrt(2gh) = sqrt(2 * 9.8 m/s² * 3 m) = 7.75 m/s (approx. 6 m/s)

Correct Answer: A — 6 m/s

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Q. A 2 kg object is dropped from a height of 20 m. What is its speed just before it hits the ground? (g = 10 m/s²) (2023)

A. 20 m/s
B. 10 m/s
C. 15 m/s
D. 5 m/s

Solution

Using the formula v = √(2gh) = √(2 * 10 m/s² * 20 m) = √400 = 20 m/s

Correct Answer: A — 20 m/s

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Q. A 2 kg object is lifted to a height of 3 m. What is the work done against gravity? (g = 9.8 m/s²) (2023)

A. 58.8 J
B. 19.6 J
C. 29.4 J
D. 39.2 J

Solution

Work Done = mgh = 2 kg * 9.8 m/s² * 3 m = 58.8 J

Correct Answer: A — 58.8 J

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Q. A 2 kg object is lifted to a height of 3 m. What is the work done against gravity? (2020)

A. 60 J
B. 30 J
C. 20 J
D. 10 J

Solution

Work Done (W) = m * g * h = 2 kg * 9.8 m/s^2 * 3 m = 58.8 J (approx. 60 J)

Correct Answer: B — 30 J

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Q. A 2 kg object is moving with a velocity of 4 m/s. What is its kinetic energy? (2023)

A. 16 J
B. 8 J
C. 4 J
D. 32 J

Solution

Kinetic Energy (KE) = 1/2 * m * v^2 = 1/2 * 2 kg * (4 m/s)^2 = 16 J.

Correct Answer: A — 16 J

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Q. A 2 kg object is moving with a velocity of 4 m/s. What is its momentum? (2020)

A. 8 kg m/s
B. 4 kg m/s
C. 2 kg m/s
D. 16 kg m/s

Solution

Momentum (p) = m * v = 2 kg * 4 m/s = 8 kg m/s

Correct Answer: A — 8 kg m/s

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Q. A 3 kg object is dropped from a height of 12 m. What is its speed just before it hits the ground? (g = 10 m/s²) (2023)

A. 15 m/s
B. 10 m/s
C. 12 m/s
D. 20 m/s

Solution

Using conservation of energy, PE = KE: mgh = 1/2 mv²; v = sqrt(2gh) = sqrt(2 * 10 m/s² * 12 m) = 15.49 m/s

Correct Answer: A — 15 m/s

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Q. A 3 kg object is lifted to a height of 4 m. What is the gravitational potential energy gained? (2023)

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

Solution

Potential Energy (PE) = m * g * h = 3 kg * 9.8 m/s^2 * 4 m = 117.6 J (approximately 120 J)

Correct Answer: A — 120 J

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Q. A 3 kg object is moving with a velocity of 2 m/s. What is its kinetic energy? (2021)

A. 6 J
B. 12 J
C. 3 J
D. 9 J

Solution

Kinetic Energy (KE) = 1/2 * m * v^2 = 1/2 * 3 kg * (2 m/s)^2 = 6 J

Correct Answer: B — 12 J

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Q. A 3 kg object is moving with a velocity of 6 m/s. What is its momentum? (2021)

A. 18 kg m/s
B. 12 kg m/s
C. 9 kg m/s
D. 6 kg m/s

Solution

Momentum (p) = mv = 3 kg * 6 m/s = 18 kg m/s

Correct Answer: A — 18 kg m/s

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Q. A 3 kg object is thrown upwards with a velocity of 15 m/s. What is its maximum height? (2020)

A. 11.5 m
B. 17.5 m
C. 22.5 m
D. 10.5 m

Solution

Using the formula v^2 = u^2 - 2gh, we find h = u^2 / (2g) = (15 m/s)^2 / (2 * 9.8 m/s²) = 11.5 m.

Correct Answer: B — 17.5 m

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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 work done on the car? (2022)

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

Solution

Work Done = Change in Kinetic Energy = 1/2 * m * (v^2 - u^2) = 1/2 * 1000 kg * (20 m/s)^2 = 200,000 J

Correct Answer: A — 200,000 J

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Q. A cyclist is moving at a speed of 10 m/s. If he doubles his speed, how much more kinetic energy will he have? (2023)

A. 4 times
B. 2 times
C. 3 times
D. 1.5 times

Solution

Kinetic Energy is proportional to the square of the speed. If speed is doubled, KE increases by a factor of 2^2 = 4.

Correct Answer: A — 4 times

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Q. A cyclist is moving with a speed of 10 m/s. If he doubles his speed, how much more kinetic energy will he have? (2023)

A. 4 times
B. 2 times
C. 3 times
D. 1.5 times

Solution

Kinetic Energy is proportional to the square of the speed. If speed is doubled, KE increases by a factor of 2^2 = 4.

Correct Answer: A — 4 times

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Q. A cyclist is moving with a speed of 15 m/s. If the mass of the cyclist and the bicycle is 75 kg, what is the kinetic energy? (2022)

A. 8437.5 J
B. 1687.5 J
C. 5625 J
D. 2250 J

Solution

Kinetic Energy (KE) = 1/2 * m * v^2 = 1/2 * 75 kg * (15 m/s)^2 = 8437.5 J.

Correct Answer: A — 8437.5 J

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Q. A spring is compressed by 0.1 m and has a spring constant of 200 N/m. What is the potential energy stored in the spring? (2019)

A. 1 J
B. 2 J
C. 0.5 J
D. 4 J

Solution

Potential Energy (PE) = 1/2 * k * x^2 = 1/2 * 200 N/m * (0.1 m)^2 = 1 J

Correct Answer: A — 1 J

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Q. A spring is compressed by 0.2 m and has a spring constant of 500 N/m. What is the potential energy stored in the spring? (2023)

A. 10 J
B. 5 J
C. 20 J
D. 2 J

Solution

Potential Energy in Spring (PE) = 1/2 kx^2 = 1/2 * 500 N/m * (0.2 m)^2 = 10 J

Correct Answer: A — 10 J

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Q. An object is dropped from a height of 20 m. What is its potential energy at the top? (2021)

A. 200 J
B. 400 J
C. 600 J
D. 800 J

Solution

Potential Energy (PE) = m * g * h = 5 kg * 9.8 m/s^2 * 20 m = 980 J (approximately 400 J for 1 kg)

Correct Answer: B — 400 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? (2021)

A. 40 J
B. 80 J
C. 100 J
D. 200 J

Solution

Work Done = m * g * h = 10 kg * 9.8 m/s² * 4 m = 392 J (approx. 400 J).

Correct Answer: B — 80 J

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Showing 1 to 30 of 39 (2 Pages)

Mechanics - Work, Energy & Power MCQ & Objective Questions

Understanding the concepts of Mechanics - Work, Energy & Power is crucial for students preparing for school and competitive exams. This topic not only forms the foundation of physics but also plays a significant role in scoring well in exams. Practicing MCQs and objective questions helps reinforce your knowledge and improves your problem-solving skills, making it easier to tackle important questions during your exam preparation.

What You Will Practise Here

Definitions and units of work, energy, and power
Work-energy theorem and its applications
Types of energy: kinetic and potential energy
Conservation of energy principle
Power calculations and its significance in mechanics
Graphical representation of work done
Real-life applications of work, energy, and power

Exam Relevance

The topic of Mechanics - Work, Energy & Power is frequently featured in CBSE, State Boards, NEET, and JEE exams. Students can expect questions that test their understanding of key concepts, numerical problems involving calculations, and application-based questions. Common patterns include direct MCQs, assertion-reason type questions, and numerical problems that require a clear grasp of formulas and definitions.

Common Mistakes Students Make

Confusing kinetic energy with potential energy
Misapplying the work-energy theorem in problem-solving
Overlooking the significance of units while calculating power
Failing to interpret graphical data related to work done
Neglecting real-world applications which can enhance understanding

FAQs

Question: What is the difference between work and energy?
Answer: Work is the transfer of energy through force applied over a distance, while energy is the capacity to do work.

Question: How is power related to work and time?
Answer: Power is defined as the rate at which work is done, calculated as work done divided by the time taken.

Now is the time to enhance your understanding of Mechanics - Work, Energy & Power. Dive into our practice MCQs and test your knowledge to excel in your exams!

Mechanics - Work, Energy & Power

Mechanics - Work, Energy & Power MCQ & Objective Questions

What You Will Practise Here

Exam Relevance

Common Mistakes Students Make

FAQs

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