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Physics (AS & A Level) · Oct / Nov 2021 · Paper 13 · Question 25

9702Doppler effect for sound waves

A train travels at constant speed along a straight track. The train’s horn emits sound of frequency 500 Hz. A person standing by the side of the track hears sound of frequency 450 Hz. The speed of sound in air is 340 m s–1. What is the speed of the train and in which direction is it travelling relative to the person?

  1. A34, away from the person
  2. B34, towards the person
  3. C38, away from the person
  4. D38, towards the person

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Correct answer: C. 38, away from the person

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