A person going away from a factory on his scooter at a speedof `36 kmh^-1` listens to the siren of the factory. If the main frequency of the siren is 600 hz and a wind is blowing alongthe direction of the scooter at `36 kmh^-1`, find the main frequency as heard by the person.

Explanation

The speed of sound instill air is `340ms^-1`. Let us work from the frame of reference of the air. As both the observer and the wind are moving at the same speed along the same direction with respect to the ground, the observer is at rest with respect to the medium. the observer is at the rest with respect to the medium. the source(the siren) is moving with respect to the wind at a speed of `36 kmh^-1` i.e. `10ms^-1`. As the source is going away from the observer who is at rest with respect to the medium, the frequency heard is
`v'=u/(v+u_s)v=340/(340+10)xx600hz583Hz`.