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AS Daily A Level Physics question

2025-12-24 OCR A Work, Energy & Power (M3) 3.3.3(a)

A lab winch lifts a 5 kg load at steady speed. In trial 1 it raises the load 1.0 m in 2.0 s. In trial 2 it raises the same load 2.0 m in 4.0 s. Ignore energy losses. Compared with trial 1, what happens to the average power output in trial 2?

  1. A It increases, because the motor lifts the load through twice the distance.
  2. B It decreases, because taking longer means a lower rate of energy transfer.
  3. C It stays the same, because both the energy transferred and the time taken double. (correct)
  4. D It becomes four times larger, because both the distance and the time change by a factor of two.

Answer

The correct answer is C.

Correct: C — It stays the same, because both the energy transferred and the time taken double. A focuses only on the increased distance and ignores that the time also doubles, leaving the rate unchanged. B is wrong because although the time is longer, the energy transferred also increases in the same proportion, so the rate does not decrease. C is correct; doubling both the energy transferred and the time leaves average power unchanged. D is a compound error that assumes effects multiply, but here the factor-of-two changes cancel rather than produce a fourfold increase.

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