In: Physics
When the bell in a clock tower rings with a sound of 500 Hz, a pigeon roosting in the belfry flies directly away from the bell. If the pigeon hears a frequency of 450 Hz, what is its speed?
Ans: 34.3 m/s
Explanation:
We know when an observer moves away from the source the frequency of the sound wave decreases due to the Doppler effect of sound.
If be the frequency of the sound emitting from the source and if be the frequency of sound after moving away some distance from the source ,then
......(1)
Here , V is the speed of sound , is the speed of pigeon , is the speed of source.
as the bell (source) is stationery , =0
For sound , V=343 m/s.
Given, and
From (1) ,
Putting given values,
So speed of the pigeon is 34.3 m/s.