Free Work and Energy MCQs with Answers
748 Work and Energy MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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Read the Work and Energy notesFree MDCAT chapter notes with key terms748 questions · page 16 of 38
- A. May increase
- B. May decrease
- C. Must increase
- D. Must decrease
Explanation: Negative work by gravity means gravity is acting opposite to displacement (lifting the body), so gravitational potential energy increases.
Correct answer: Must increase- A. Remain same
- B. Be doubled
- C. Be quadrupled
- D. Be half
Explanation: K = p²/(2m). If K → 4K, then p² → 4 p² ⇒ p → 2 p. Hence momentum doubles when kinetic energy is quadrupled.
Correct answer: Be doubled- A. 10 J
- B. 100 J
- C. Zero
- D. Infinite
Explanation: Work W = F d cosθ; here θ = 90°, cos90° = 0, so W = 10×10×0 = 0 J. A force perpendicular to displacement does no work.
Correct answer: Zero- A. v = √gh
- B. v = √2gh
- C. v = √(gh/2)
- D. v = 2√gh
Explanation: Half P.E. lost ⇒ KE = ½ mgh ⇒ ½ m v² = ½ m g h ⇒ v² = g h ⇒v = √(gh). So option A is correct.
Correct answer: v = √gh- A. K.E. only
- B. P.E. only
- C. K.E. and P.E. both
- D. All may be correct
Explanation: The work-energy theorem states that the net work equals change in kinetic energy.
Correct answer: K.E. only- A. 0
- B. 900J
- C. 600J
- D. 400J
Explanation: Holding stationary means zero displacement of the weight in direction of the force, so the work done by the boy's force is zero despite…
Correct answer: 0- A. 5/9.8 J
- B. 500 x 20 J
- C. 500/9.8 J
- D. 500/20/9.8 J
Explanation: Increase in gravitational potential energy = weight × height = 500 N × 20 m = 10,000 J. Option B matches this product.
Correct answer: 500 x 20 J- A. Double
- B. 1/4 times
- C. Half
- D. 4 times
Explanation: Work W = F d. If F → 2F and d → 2d then W → (2F)(2d) = 4 F d, i.e., four times the original work.
Correct answer: 4 times- A. Truck will cover less distance before stopping
- B. Car will cover less distance before stopping
- C. Both will cover equal distance
- D. None of the mentioned
Explanation: For same initial speed, stopping distance under same retarding force depends on mass via kinetic energy; the heavier truck stores more KE…
Correct answer: Car will cover less distance before stopping- A. 2mgh
- B. 3mgh
- C. 4mgh
- D. 6mgh
Explanation: W=mg(0h)+mg(1h)+mg(2h)+mg(3h) = 0+mgh+2mgh+3mgh= 6mgh
Correct answer: 6mgh- A. 5000 J
- B. 9000 J
- C. 900 J
- D. 500 J
Explanation: Efficiency = output/input. Input = output/efficiency = 4500J / 0.5 = 9000 J. Thus option B is correct.
Correct answer: 9000 J- A. 3 times
- B. 9 times
- C. 27 times
- D. 81 times
Explanation: For fixed head and time, power ∝ mass flow rate. To triple the delivered mass, power must be tripled. Hence, option A is correct.
Correct answer: 3 times- A. 100 J
- B. 150 J
- C. 200 J
- D. 192 J
Explanation: Momentum conservation: 0 = 8×5 + 4 v4 ⇒ v4 = −(8×5)/4 = −10 m/s (opposite direction). K.E. of 4 kg = ½×4×10² = 200 J.
Correct answer: 200 J- A. 19%
- B. 21%
- C. 36%
- D. 42%
Explanation: K ∝ p² (since K = p²/(2m)). If p → 0.8 p, then K → (0.8)² K = 0.64 K, a 36% decrease. Thus, option C is correct.
Correct answer: 36%- A. 6 watt
- B. 18 watt
- C. 3 watt
- D. 1 watt
Explanation: Power = work/time = 3 J / 3 s = 1 W. Therefore, option D is correct.
Correct answer: 1 watt- A. Friction
- B. Gravitational
- C. Electric
- D. Elastic spring force
Explanation: Friction is path-dependent and dissipative; work done by friction depends on the path, so it is non‑conservative.
Correct answer: Friction- A. 14000 √3 m/sec
- B. 20 sin 30° m/sec
- C. 1.4 m/sec
- D. 14 m/sec
Explanation: Vertical drop h = 20 sin30° = 10 m. Using v = √(2 g h) with g ≈10 m/s² gives v = √(2×10×10) = √200 ≈ 14 m/s. So option D is correct.
Correct answer: 14 m/sec- A. mgh + mv2
- B. mgh - mv²
- C. mgh + ½ mv²
- D. mgh - ½ mv²
Explanation: When a body falls freely, its kinetic energy increases while its potential energy decreases.
Correct answer: mgh + ½ mv²- A. Work is constant regardless of the angle
- B. Work is maximum when the angle is 0°
- C. Work is negative when the angle is 90°
- D. Work is 0 when the angle is 45°
Explanation: Work is maximum when angle is zero because cos 0 is 1.
Correct answer: Work is maximum when the angle is 0°- A. 0.5 F
- B. 0.866 F
- C. Fcos30°
- D. 0.707 F
Explanation: Horizontal component = F cos60° = 0.5 F. This component does the horizontal work over the 10 m, so option A is correct.
Correct answer: 0.5 F