Wave Motion 4 Question 24

23. An observer standing on a railway crossing receives frequency of 2.2kHz and 1.8kHz when the train approaches and recedes from the observer. Find the velocity of the train. (The speed of the sound in air is 300m/s.)

(2005, 2M)

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Answer:

Correct Answer: 23. vT=30 m/s

Solution:

  1. From the relation, f=f(vv±vs), we have 2.2=f[300300vT](i)and1.8=f[300300+vT](ii)

Here, vT=vs= velocity of source/train

Solving Eqs. (i) and (ii), we get vT=30 m/s



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