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 17 of 38
- A. 38.2 J
- B. 39.2 J
- C. 392.1 J
- D. 3.92 J
Explanation: Work = mgh = 2 × 9.8 × 2 = 39.2 J. Thus option B is correct.
Correct answer: 39.2 J- A. 300 N-m
- B. 420 N-m
- C. 720 N-m
- D. None of these
Explanation: Gravity does work only for vertical displacement: W = −mg Δh = −60×5 = −300 J (magnitude 300 N·m).
Correct answer: 300 N-m- A. 5.0 kW
- B. 2.5 kW
- C. 10 kW
- D. 12.5 kW
Explanation: Power = force × velocity = 500 N × 5 m/s = 2500 W = 2.5 kW. Therefore option B is correct.
Correct answer: 2.5 kW- A. Zero
- B. Negative
- C. Maximum
- D. Minimum
Explanation: Work W = F d cosθ is maximized when θ = 0° (cos θ = 1), i.e., force parallel to displacement, so the work is maximum.
Correct answer: Maximum- A. 1 hp
- B. 2 hp
- C. 3 hp
- D. 4 hp
Explanation: Power = 9000 J / 3 s = 3000 W. In horsepower 3000/746 ≈ 4.02 hp, approximately 4 hp. Hence option D.
Correct answer: 4 hp- A. Gm/R
- B. Gm/R²
- C. GmM/R
- D. GmM/R²
Explanation: Gravitational potential energy of mass m at distance R from Earth's center is U = −GMm/R; the magnitude uses GMm/R, so option C (G M m /…
Correct answer: GmM/R- A. Coal
- B. Uranium
- C. Oil
- D. Gas
Explanation: Uranium is a radioactive element used as nuclear fuel, not formed from the remains of ancient plants or animals.
Correct answer: Uranium328. If a 1000 kg car accelerates from rest to 20 m/s in 5 seconds, what is the average power delivered?
- A. 4000 W
- B. 8000 W
- C. 40000 W
- D. 80000 W
Explanation: Work = ΔKE = ½mv² = ½ × 1000 × 20² = 200000 J. Power = Work / Time = 200000 / 5 = 40000 W.
Correct answer: 40000 W- A. Parallel
- B. Anti-parallel
- C. Perpendicular
- D. At 45o
Explanation: Work W = F d cosθ is negative when cosθ < 0; this occurs when θ = 180°, i.e., force and displacement are opposite (anti‑parallel).
Correct answer: Anti-parallel- A. 2 J
- B. 200 kJ
- C. 200 J
- D. 2 kJ
Explanation: Use formula K.E = ½ mv² for both speeds separately.½ mv²½ (800)(30)² = 360000--------- ½ mv²½ (800)(20)² = 160000Change in K.E = 360000 -…
Correct answer: 200 kJ- A. 1410 ms-1
- B. 141 ms-1
- C. 1.41 ms-1
- D. 9800 ms-1
Explanation: Using v = √(2 g h) with g ≈ 10 m/s², v = √(2×10×1000) = √20000 ≈ 141 m/s. Thus, option B is correct.
Correct answer: 141 ms-1- A. 1 mg
- B. 3 mg
- C. 2 mg
- D. 0
Explanation: Object m displaced from A to B, both at the same height hence potential energy is zero.
Correct answer: 0- A. 5 x 10⁷ J
- B. 5 x 10⁻² J
- C. 5 x 10⁸ J
- D. 5 x 10⁰ J
Explanation: Using KE = ½ p v with SI units: convert v = 10000 cm/s = 100 m/s, p = 10000 g·cm/s = 0.1 kg·m/s (better: p in SI = 10,000 g·cm/s = 0.1…
Correct answer: 5 x 10⁰ J334. One erg is equal to:
- A. 10⁻⁵ dynes
- B. 10⁻⁷ watt
- C. 10⁻⁷ joules
- D. 10⁻⁵ newton
Explanation: By definition 1 erg = 10⁻⁷ J. Thus option C is correct.
Correct answer: 10⁻⁷ joules- A. Is positive
- B. Is negative
- C. Is zero
- D. Depends for its sign on the direction of the y axis
Explanation: During descent gravity and displacement are in the same direction (downward), so the work done by gravity is positive.
Correct answer: Is positive- A. watt second
- B. kg m²/s²
- C. gram.cm/s²
- D. ft lb
Explanation: Gram ·cm/s² is a unit of force (dyne), not energy. The others (W·s = J, kg·m²/s² = J, ft·lb are energy units).
Correct answer: gram.cm/s²- A. 0.98 J
- B. 9.8 J
- C. 98 J
- D. 980 J
Explanation: m = 0.1 kg, PE = m g h = 0.1×9.8×100 = 98 J. Hence option C is correct.
Correct answer: 98 J- A. W2 = W1
- B. W2 = 9W1
- C. W1 = 3 W2
- D. W2 = 3W1
Explanation: Elastic work W = ½ k x². With same x, W ∝ k. If k₂ = 3k₁ then W₂ = 3 W₁. Hence option D.
Correct answer: W2 = 3W1- A. 500 J
- B. 3 kJ
- C. 5 kJ
- D. 30 kJ
Explanation: Energy per minute = Power × time = 500 W × 60 s = 30000 J = 30 kJ. Thus option D is correct.
Correct answer: 30 kJ- A. 245 J
- B. 49 J
- C. 25 J
- D. 98 J
Explanation: Work = mgh = 5×9.8×5 = 245 J. Therefore option A is correct.
Correct answer: 245 J