Work, Energy and Power — Class 11 MCQs with Answers
Class 11 CBSE Physics · Chapter 6
66 practice questions · 22 Easy · 22 Medium · 22 Hard · Updated
Practise the most important Class 11 CBSE Physics questions from Chapter 6, "Work, Energy and Power". You get 6 timed quizzes made from 66 NCERT-based MCQs, with answers and explanations. The questions are split into 22 Easy, 22 Medium and 22 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG apart.
To score well in "Work, Energy and Power", focus on numericals, derivations and applying concepts. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Work, Energy and Power, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 11 Physics mastery score. 13 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Work, Energy and Power (Class 11 Physics)
Work as the transfer of energy, the work-energy theorem linking net work to change in kinetic energy, potential energy for gravity and springs, the distinction between conservative and non-conservative forces, conservation of mechanical energy, power, and the classification of collisions by what is conserved.
- Work done by a constant force
- The product of force, displacement and the cosine of the angle between them. Work is a scalar even though both force and displacement are vectors.
- Positive, negative and zero work
- Work is positive when the force has a component along the displacement, negative when opposed, and zero when the force is perpendicular to the motion.
- Work done by a variable force
- Found as the area under the force-displacement graph, or the integral of F dx. This is how spring work and non-uniform force problems are handled.
- Kinetic energy
- The energy a body has by virtue of its motion, equal to ½mv². It is always positive and can also be written as p²/2m in terms of momentum.
Work, Energy and Power — important questions & MCQs with answers (Class 11 Physics)
13 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 53 are timed and scored when you sign in.
- Q1Easy
SI unit of work and energy:
A.NewtonB.PascalC.WattD.Joule✓ CorrectAnswer: D. Joule
Explanation: Work and energy share the SI unit joule (1 J = 1 N·m), same as PE and KE. Watt is the unit of power (J/s), not energy — that mix-up is the tempting wrong pick here.
- Q2Easy
Work W = ?
A.F · d cos θ✓ CorrectB.F + dC.F − dD.F · d sin θAnswer: A. F · d cos θ
Explanation: Work is the dot product of force and displacement, W = F·d·cosθ, picking out only the component of force along the displacement. Writing F·d sinθ instead confuses it with the cross product used for torque.
- Q3Easy
Kinetic energy KE = ?
A.mv²B.mvC.(1/2)mv²✓ CorrectD.(1/2)mghAnswer: C. (1/2)mv²
Explanation: Kinetic energy is KE = ½mv², derived from the work-energy theorem applied to constant acceleration. mv² (dropping the ½) is the classic slip that doubles the true value — always keep the factor of ½.
- Q4Easy
Gravitational PE near surface = ?
A.mgh²B.mgh✓ CorrectC.(1/2)mghD.mg/hAnswer: B. mgh
Explanation: Gravitational PE near Earth's surface is U = mgh, linear in height h. mgh² would make PE grow quadratically with height, which has no physical basis — the ½ factor and squared-h both belong to other formulas, not to gravity's PE.
- Q5Easy
Power = ?
A.Work/time = F·v✓ CorrectB.FC.ForceD.EnergyAnswer: A. Work/time = F·v
Explanation: Power is the rate of doing work, P = W/t, which for a constant force along the velocity direction becomes P = F·v. Force alone (F) has no time dimension and isn't power — that's the common confusion.
- Q6Medium
SI unit of power:
A.JouleB.PascalC.NewtonD.Watt (J/s)✓ CorrectAnswer: D. Watt (J/s)
Explanation: Power is the rate of doing work, P = W/t, so its SI unit is the watt, 1 W = 1 J/s. Joule is energy, not power — swapping the two is the usual trap in unit questions.
- Q7Medium
Force 10 N applied over 5 m at angle 0° to displacement. Work done:
A.10 JB.50 J✓ CorrectC.5 JD.ZeroAnswer: B. 50 J
Explanation: Work is W = Fd cosθ = 10 N × 5 m × cos0° = 10 × 5 × 1 = 50 J, since the force acts fully along the displacement. Picking 10 J confuses the force value alone with the actual work done.
- Q8Medium
KE of 2 kg body at 5 m/s:
A.25 J✓ CorrectB.10 JC.50 JD.100 JAnswer: A. 25 J
Explanation: Kinetic energy is KE = ½mv² = ½ × 2 kg × (5 m/s)² = ½ × 2 × 25 = 25 J. Forgetting to square the velocity gives 10 J (½ × 2 × 5), a common slip when the numbers look easy to multiply straight through.
- Q9Medium
PE of 5 kg body at height 10 m (g = 10):
A.250 JB.50 JC.500 J✓ CorrectD.1000 JAnswer: C. 500 J
Explanation: Gravitational PE is U = mgh = 5 kg × 10 m/s² × 10 m = 500 J, using g = 10 m/s² as stated. Multiplying only mg (= 50) without the extra factor of h gives 50 J, missing the height entirely.
- Q10Medium
Engine does 1500 J of work in 5 s. Power:
A.1500 WB.30 WC.100 WD.300 W✓ CorrectAnswer: D. 300 W
Explanation: Power is P = W/t = 1500 J / 5 s = 300 W. Dividing the other way (5/1500) or just quoting the work value as 1500 W both ignore that power is work per unit time, not work itself.
- Q11Hard
Body of 1 kg fired vertically with velocity 20 m/s. At 10 m height, KE (g = 10):
A.100 J✓ CorrectB.200 JC.ZeroD.50 JAnswer: A. 100 J
Explanation: Initial KE is ½ × 1 × 20² = 200 J; at 10 m height, PE used up is mgh = 1 × 10 × 10 = 100 J, so by energy conservation the remaining KE = 200 − 100 = 100 J. Forgetting to subtract the PE gained and keeping the full 200 J is the tempting error.
- Q12Hard
Variable force F(x) = 2x N over x from 0 to 5 m. Work done:
A.50 JB.25 J✓ CorrectC.10 JD.5 JAnswer: B. 25 J
Explanation: For a variable force, work is the integral W = ∫F(x)dx = ∫₀⁵ 2x dx = [x²]₀⁵ = 25 − 0 = 25 J. Treating F as constant and multiplying the endpoint force (2×5=10 N) by the distance would wrongly give 50 J.
- Q13Hard
KE of body at speed v is K. At speed v/2, KE:
A.K/4✓ CorrectB.K/2C.KD.2KAnswer: A. K/4
Explanation: Since KE ∝ v², halving the speed to v/2 scales kinetic energy by (1/2)² = 1/4, giving K/4. Assuming KE simply halves along with speed, landing on K/2, ignores that velocity enters the formula squared.
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Start this chapter free →Work, Energy and Power — FAQs
What are the key concepts in Class 11 Physics Work, Energy and Power?+
Work as the transfer of energy, the work-energy theorem linking net work to change in kinetic energy, potential energy for gravity and springs, the distinction between conservative and non-conservative forces, conservation of mechanical energy, power, and the classification of collisions by what is conserved. Key ideas include Work done by a constant force, Positive, negative and zero work, Work done by a variable force, Kinetic energy.
What does Class 11 Physics Chapter 6 (Work, Energy and Power) cover on XamBaaz?+
It has 66 NCERT-based MCQs on "Work, Energy and Power": 22 Easy, 22 Medium and 22 Hard. Together they make 6 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG.
Are these "Work, Energy and Power" questions free to practise?+
Yes. Sign in with Google to practise "Work, Energy and Power" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Work, Energy and Power" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 6 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Work, Energy and Power" MCQs available with answers?+
Yes. 13 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Work, Energy and Power" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip, the same negative marking as JEE Main, JEE Advanced and NEET UG. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Work, Energy and Power (Class 11 Physics)?+
The questions that matter most test Work done by a constant force, Positive, negative and zero work, Work done by a variable force, Kinetic energy. This page shows 13 solved important MCQs with answers and explanations; all 66 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Work, Energy and Power?+
Yes — Class 11 Physics Work, Energy and Power has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.