A person carrying a whistle emitting continuously a note of 272 Hz is running towards a reflecting surface with a speed of 18 `kmh^(-1)`. The speed of sound in air is `345ms^(-1)`. The number of beats heard by him is

Answer

8

Explanation

`n=272,v_(s)=5m//s,v_(L)=5m//s,v=345m//s`
`n.=((v+v_(L))/(v-v_(s)))n,n.=((345+5)/(345-5))272=(350xx272)/(340)=280`
No. of beats=280-272=8