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A train moves towards a stationary obser...

A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observe is `f_1`. If the train'sspeed is reduced to 17 m/s, the frequency registered is `f_2` If the speed of sound is 340 m/s, then find the ratio `f_1//f_2` .

Text Solution

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For the stationary observer `f_1 = v/(v-v_s)xxf`
`:. F_1 = 340/(340 - 34) xx f and f_2 = 340/(340-17) xx f`
Hence `f_2/f_1 = (340-17)/(340-34)= 19/18 rArr f_1 : f_2 = 19 : 18`
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