# Q. A train is approaching towards a platform with a speed of $10\,ms^{-1}$ while blowing a whistle of frequency 340 Hz. What is the frequency of whistle heard by a stationary observer on the platform ? Given speed of sound = 340 $ms^{-1}$.

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Solution:

## $f'=f\left(\frac{V}{V-V_s}\right)\implies \,f'=340\left(\frac{340}{340-10}\right)$= $\frac{340\times340}{30}=350.3\,Hz$

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