FSc Part 1 Physics chapter 4: Work and energy MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

28 exam-style questions on Work and energy, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

28 questions · 3 topics · 10 per test

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What chapter 4 covers

Ten Work and energy questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. The main fuel gas in biogas, produced when animal dung decays in a closed digester, is

  1. A
    hydrogen
  2. B
    carbon monoxide
  3. C
    methane
  4. D
    ethanol
Show answer

Answer: C. Anaerobic decay of biomass produces biogas, which is mostly methane with some carbon dioxide. Ethanol is a liquid made by fermentation.

2. A ball is dropped from a height of 20 m. Ignoring air resistance, its speed just before hitting the ground is

  1. A
    14.0 m s−1
  2. B
    9.9 m s−1
  3. C
    19.8 m s−1
  4. D
    392 m s−1
Show answer

Answer: C. ½mv2 = mgh, so v = √(2gh) = √(2 × 9.8 × 20) = √392 = 19.8 m s−1. 14.0 m s−1 misses the factor 2.

3. Taking g = 9.8 m s−2 and R = 6.4 × 106 m, the escape velocity from the Earth is about

  1. A
    7.9 km s−1
  2. B
    9.8 km s−1
  3. C
    11.2 km s−1
  4. D
    25 km s−1
Show answer

Answer: C. v = √(2gR) = √(2 × 9.8 × 6.4 × 106) = √(1.25 × 108) ≈ 1.12 × 104 m s−1 = 11.2 km s−1. 7.9 km s−1 is the orbital speed.

4. The escape velocity from the surface of a planet of radius R and surface gravity g is

  1. A
    √(gR)
  2. B
    √(gR/2)
  3. C
    2gR
  4. D
    √(2gR)
Show answer

Answer: D. ½mv2 = GMm/R gives v = √(2GM/R) = √(2gR), since GM = gR2. √(gR) is the orbital speed just above the surface.

5. Two bodies of masses m and 4m have equal momentum. The ratio of their kinetic energies (lighter : heavier) is

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

Answer: D. K.E. = p2/2m. With equal p, K.E. ∝ 1/m, so the lighter body has 4 times the K.E.: 4 : 1.

6. The force on a spring rises uniformly from 0 to 40 N as it is stretched by 0.50 m. The work done in stretching it is

  1. A
    20 J
  2. B
    10 J
  3. C
    40 J
  4. D
    80 J
Show answer

Answer: B. Work = area under the force-extension graph = ½ × 40 × 0.50 = 10 J. 20 J treats the force as constant at 40 N.

7. Tidal energy is obtained mainly because of

  1. A
    the gravitational pull of the Moon (and Sun) on the ocean water
  2. B
    heat from the Earth's core
  3. C
    winds blowing over the sea
  4. D
    the evaporation of sea water by sunlight
Show answer

Answer: A. The Moon's gravity (and to a lesser extent the Sun's) raises and lowers sea levels twice a day; the moving water can drive turbines.

8. Why is the absolute potential energy of a body in the Earth's gravitational field negative?

  1. A
    because the gravitational force becomes repulsive at large distances
  2. B
    because potential energy is taken as zero at the Earth's surface
  3. C
    because it is zero at infinity and the force is attractive, so work must be done to take the body to infinity
  4. D
    because r is measured from the Earth's surface
Show answer

Answer: C. With U = 0 at infinity, energy must be supplied to pull the body away against the attractive force, so everywhere closer U is less than zero.

9. A pendulum bob is released from rest 0.45 m above its lowest point. Ignoring air resistance, its speed at the lowest point is

  1. A
    2.97 m s−1
  2. B
    4.41 m s−1
  3. C
    8.82 m s−1
  4. D
    2.10 m s−1
Show answer

Answer: A. v = √(2gh) = √(2 × 9.8 × 0.45) = √8.82 = 2.97 m s−1. The mass cancels, and 8.82 is v2, not v.

10. A 2.0 kg mass is lifted from point A to point B, 5.0 m higher, once straight up and once along a long smooth ramp. The work done against gravity

  1. A
    is greater along the ramp because the path is longer
  2. B
    is smaller along the ramp because less force is needed
  3. C
    is 10 J by both routes
  4. D
    is 98 J by both routes
Show answer

Answer: D. Gravity is conservative, so the work depends only on the height gained: mgh = 2.0 × 9.8 × 5.0 = 98 J by any path. The ramp needs less force over a longer distance.

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Ways to practise this chapter

Work and energy: questions students ask

How many Work and energy MCQs are there?

28, each with the answer and a short explanation, across 3 topics: Work, power and conservative field, Work-energy principle and conservation of energy, Absolute potential energy, escape velocity and energy sources. Every chapter test draws ten of them, so you can take it many times.

Is the FSc Part 1 Physics chapter 4 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

Can I read the explanations in Urdu?

Yes. In practice mode and on your results you can switch the explanations to Urdu.

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