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A train standing at the outer signal of ...

A train standing at the outer signal of a railway station blows a whistle of frequency 400Hz in still air. (i) What is the frequency of the whistle for a platform observer when the train (a) approaches the platform with a speed of `10 ms^(-1)`. (b) recedes from the platform with a speed of `10ms^(-1)` ? (ii) What is the speed of sound in each case? The speed of sound in still air can be taken as `340ms^(-1)`.

Text Solution

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We have `(f _(L))/( v + v _(L)) = (f _(S))/( v + v _(S))`
`therefore (f _(L ))/( 330 + 0) =(400)/(330 -10)`
`therefore f_(L) = 400 xx (330)/(320) =412.5 z.`
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