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The siren of a train, moving at a constant speed along a straight horizontal track, emits
sound with a constant frequency. A detector, placed next to the track, records the
frequency of the sound waves. The results obtained are as shown in the graph below.
6.1 State the Doppler effect in words. (2)
6.2 Does the detector record the frequency of 3 148 Hz when the train moves
TOWARDS the detector or AWAY from the detector? (1)
6.3 Calculate the speed of the train. Take the speed of sound in air as 340 m∙s-1. (6)
6.4 The detector started recording the frequency of the moving train’s siren when
the train was 350 m away.
Calculate time t1 indicated on the graph above. (2)
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