A bullet passes past a person at a speed of `220 m s^-1`. Find the fractional change in the frequency of the whistling sound heard by the person as the bullet crosses the person. Speed of sound in air `= 330 m s^-1`.

Explanation

`{:(rarr v_(s),=220m//s,rarr v_(o)=0),(overset(*)(S),,overset(*)(O)),(,rarrv,):}`
When bullet is coming towards person, apparent frequency
`f_(1) = f((v)/(v - v_(s))) = f((330)/(330 - 220)) = 3 f`
`{:(rarr v_(o)=0,,rarr v_(s)=220 m//s),(overset(*)(O),,overset(*)(S)),(,rarrv,):}`
When bullet is moving away, apparent frequency
`f_(2) = f((v)/(v + v_(s))) = f((330)/(330 - 220)) = (3f)/(5)`
Fractional change `= (f_(2))/(f_(1)) - 1 = (1)/(5) - 1 = (1)/(5) = - 0.8`