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 19 of 38
- A. Joule
- B. erg
- C. kWh
- D. All of these
Explanation: "All of these are units of energy. The most commonly used unit is Joules, however erg is also a unit of energy and it is equal to 10⁻⁷…
Correct answer: All of these- A. 100 J
- B. 200 J
- C. 300 J
- D. 400 J
Explanation: ΔKE = ½ m (v₂² − v₁²) = 0.5×10×(64−4) = 5×60 = 300 J. Thus option C.
Correct answer: 300 J- A. Hydro power
- B. Wind power
- C. Tidal power
- D. Biomass power
Explanation: In some contexts "conventional" refers to long‑established methods; biomass has been used historically as a traditional energy source, so…
Correct answer: Biomass power- A. 3.6 × 10⁷ J
- B. 3.6 × 10⁹ J
- C. 3.6 × 10¹² J
- D. 3.6 × 10¹⁸ J
Explanation: 1 MWh = 10 W × 3600 s = 3.6×109 J. Thus option B is correct.
Correct answer: 3.6 × 10⁹ J- A. 100 J
- B. 173 J
- C. 200 J
- D. 346 J
Explanation: Work = F × d × cosθ = 20 × 10 × cos30° = 20 × 10 × (√3/2) ≈ 173 J.
Correct answer: 173 J366. What is the power output of a machine that lifts a 100 kg object 5 m in 10 seconds? (g = 9.8 m/s²)
- A. 49 W
- B. 98 W
- C. 490 W
- D. 980 W
Explanation: Work = mgh = 100 × 9.8 × 5 = 4900 J. Power = Work / Time = 4900 / 10 = 490 W.
Correct answer: 490 W- A. 200 J
- B. 400 J
- C. 600 J
- D. 800 J
Explanation: At maximum height, kinetic energy (½mv² = ½ × 2 × 20² = 400 J) converts to potential energy, so PE = 400 J.
Correct answer: 400 J368. A spring with constant k = 200 N/m is compressed by 0.1 m. What is the potential energy stored?
- A. 0.5 J
- B. 1.0 J
- C. 2.0 J
- D. 4.0 J
Explanation: Spring potential energy = ½kx² = ½ × 200 × (0.1)² = ½ × 200 × 0.01 = 1.0 J.
Correct answer: 1.0 J369. A body is displaced in a gravitational field as shown in the figure. The work done from A to C is:
- A. Greater than the work done from A to C via B
- B. Less than the work done from A to C via B
- C. Equal to the work done from A to C via B
- D. Double the work done from A to C via B
Explanation: Work done by gravity from A to C along two paths= Equal to the work done from A to C via B.
Correct answer: Equal to the work done from A to C via B- A. 5.4 m/s
- B. 7.7 m/s
- C. 9.8 m/s
- D. 12.1 m/s
Explanation: Using conservation of energy, mgh = ½mv². Cancel m: v² = 2gh = 2 × 9.8 × 3 = 58.8, v = √58.8 ≈ 7.7 m/s.
Correct answer: 7.7 m/s- A. 300 J
- B. 18000 J
- C. 3600 J
- D. 7200 J
Explanation: Energy = Power × Time = 60 × (5 × 60) = 60 × 300 = 18000 J.
Correct answer: 18000 J- A. 25 N
- B. 50 N
- C. 75 N
- D. 100 N
Explanation: Work = F × d × cosθ. Here, θ = 0° (force parallel to incline), so 200 = F × 4 × 1, F = 200 / 4 = 50 N.
Correct answer: 50 N- A. 5000 J
- B. 49000 J
- C. 50625 J
- D. 99000 J
Explanation: Total energy = PE + KE = mgh + ½mv² = (500 × 9.8 × 20) + (½ × 500 × 5²) = 98000 + 6250 = 104250 J (closest to 99000 J, assuming option…
Correct answer: 99000 J374. When the output power equals to one-half of the input power, efficiency of the transformer becomes:
- A. 0%
- B. 100%
- C. 50%
- D. 200%
Explanation: The following is the solution:Following is the formula for efficiency. As we can plug in values of input and output, we will get 50%.
Correct answer: 50%375. A mass of 20 kg is lifted from the floor to a height of 2m in 4.9 sec. Calculate the power in Watts:
- A. 60 W
- B. 80 W
- C. 100 W
- D. 120 W
Explanation: The formula for calculating power, P is:P=mgh/tWhere m is the mass, g is the gravitational acceleration, h is the height and t is the…
Correct answer: 80 W- A. Pushing a car to start it moving
- B. Lifting the weights
- C. The moon orbiting the Earth
- D. Writing an essay on a page
- E. C and D
Explanation: When you lift weights, you apply a force (the gravitational force) to move the weights against gravity.
Correct answer: C and D- A. Electrical energy
- B. Losses
- C. Gains
- D. Wind energy
- E. Nothing
Explanation: When coal or petrol is burnt chemical energy stored in it is converted to heat energy and some of it is lost to the surrounding.
Correct answer: Losses- A. 37.702 x 10^-19 joule
- B. 27.702 x 10^-19 joule
- C. 17.70 x 10^-19 joule
- D. 07.702 x 10^-29 joule
Explanation: The following is the solution:speed of neutron = distance travelled by neutron / time taken by neutron for covered that distance .speed of…
Correct answer: 37.702 x 10^-19 joule- A. Electric Energy
- B. Power
- C. Momentum
- D. Torque
Explanation: The kilowatt-hour (SI symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy equal to 3600 kilojoules (3.6 megajoules).
Correct answer: Electric Energy380. The sum of all forms of molecular energies (kinetic and potential) of a substance is termed as:
- A. Elastic energy
- B. Absolute energy
- C. Internal energy
- D. Heat energy
Explanation: Elastic energy is a form of potential energy. Absolute energy does not exist.
Correct answer: Internal energy