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Class XI · Physics

Work, Energy and Power: NEET MCQ practice

135 practice questions on Work, Energy and Power, each with an explanation. Practise them chapter by chapter in the GyaanLoop app.

135

Practice questions

77

Easy

57

Medium

1

Hard

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What Work, Energy and Power covers

Topics in the NEET (UG) 2026–27 syllabus for this chapter.

  • Work done by constant and variable force
  • Kinetic and potential energy, work-energy theorem, power
  • Potential energy of spring, conservation of mechanical energy
  • Conservative and non-conservative forces
  • Elastic and inelastic collisions in one and two dimensions

Sample questions on Work, Energy and Power

Try each one, then open the answer and explanation.

Question 1 · Practice question

How should the force applied on a body be varied with velocity to keep the power of force constant?

  1. A.Force should be inversely proportional to the square root of the velocity of the body
  2. B.Force should be inversely proportional to the velocity of the body
  3. C.Force should be directly proportional to the velocity of the body
  4. D.Force should not be varied. It should remain constant with the velocity
Show answer

Answer: B. Force should be inversely proportional to the velocity of the body

Power is defined as P = F·v for constant force in the direction of motion. To keep P constant, F must vary so that F·v remains constant, which means F ∝ 1/v. Option C is wrong because if F ∝ v, then P ∝ v², which changes with velocity. Option D is wrong because constant force would mean P ∝ v.

Question 2 · Practice question

An engine generates a power of 10 kW. In how much time will it raise a mass of 200 kg through a height of 40m.

  1. A.4 sec
  2. B.10 sec
  3. C.5 sec
  4. D.8 sec
Show answer

Answer: D. 8 sec

Power is work done per unit time. The work needed to lift the mass is mgh, which equals 80,000 J. Dividing by 10,000 W gives 8 s. A student might misremember formulas or forget unit conversion (kW to W).

Question 3 · Practice question

A person 'A' pushes a body of 5 kg placed on a rough surface of co-efficient of friction 0.3 by a distance of 4 m in 15 seconds. Another person 'B' pushes the body of 7 kg on same surface by a distance of 3 m in the same time. Who has more energy and power?

  1. A.A
  2. B.B
  3. C.Both A and B have developed equal power but B has more energy
  4. D.Both A and B have developed equal power but A has more energy
Show answer

Answer: B. B

Assuming the body moves uniformly against kinetic friction, the force applied by each person equals frictional force F = μ mg. Work done (energy spent) is W = μ mg d, and power is P = W/t. Since μ, g, and t are same, comparing m × d shows B: 7×3=21 > A: 5×4=20, so B does more work and hence more power. Option (b) is correct. Others are wrong because they incorrectly assume equal power, but power differs as work differs.

Question 4 · Practice question

A man A of mass 80 kg runs up a staircase in 12 seconds. Another man of mass 60 kg runs up the same staircase in 11 seconds. The ratio of powers of A and B is :

  1. A.11:12
  2. B.9:11
  3. C.12:11
  4. D.11:9
Show answer

Answer: D. 11:9

Power for climbing is mg (change in height) / time = mgh/t. Same h means power ratio = (m(A) / t(A)) : (m(B) / t(B)). Direct substitution gives (80/12):(60/11) = (20/3):(60/11) = 11:9 after simplification. Distractor 11:12 forgets mass differences; 12:11 swaps the ratio incorrectly.

Question 5 · Practice question

If momentum of an object is doubled, how does its kinetic energy change?

  1. A.increases 4 times
  2. B.increases 2 times
  3. C.decreases 4 times
  4. D.decreases 2 times
Show answer

Answer: A. increases 4 times

Kinetic energy is proportional to the square of momentum (K ∝ p²). Doubling momentum means kinetic energy becomes 2² = 4 times the original. Option (b) 'increases 2 times' would be correct if kinetic energy were directly proportional to momentum, which is a common misconception.

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