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A trian standing at the outer signal of ...

A trian standing at the outer signal of a railway station belows a whistle of frequency 400 Hz still air. The train begins to move with a speed of `10ms^(-1)` towards the platform. What is the frequecncy of the sound for and obeserver standing on the platform? (sound velocity in air `330 ms^(-1))`

Text Solution

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As the source (train) is moving towards the observer (plantform) hence apparent frequency observed is more than the naturela frequecy .
Frequency of whitle `" " v=400 Hz`
Speed of train `" " v_(1)=10 m//s`
Velocity of sound in air `" " v=330 m//s`
Apparent frequency when source is moving `v_("app")((v)/(v-v_(1)))`
`" =((330)/(330-10))400`
`rArr" "v_("app")=(330)/(320)xx400=412.5Hz`
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