A sparrow chases a crow with a speed of 4.0 m/s, while chirping at a frequency of 850.0 Hz. What frequency of sound does the crow hear as he flies away from the sparrow with a speed of 3.0 m/s?

1 Answer
Trevor Ryan.
Oct 29, 2015

#832,653Hz#

Explanation:

By the Doppler effect of sound waves, the new frequency#f'# observed is given by

#f'=f((v+-v_o)/(v+-v_s))#,

where #f'>f# for relative motion of source and observer towards each other and #f'<f# for relative motion of source and observer away from each other.

So in this particular case, and taking the speed of sound in air to be #v=340m//s#, and assuming the speed of the crow is 4m/s and that of the sparrow 3m/s (as question is a bit unclear), we get

#f'=850((340-4)/(340+3))=832,653Hz#

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