Two cars are moving on two perpendicular road towards a crossing with uniform speeds of `72km//hr` and `36km//hr`. If first car blows horn of frequency 280 Hz, then the frequency of horn heard by the driver of second car when line joining the cars make `45^@` angle with the roads, will be

Options

A. `321 Hz`
B. `298 Hz`
C. `289 Hz`
D. `280 Hz`

Answer

B

Explanation

`f' = f((v+v_(o) cos 45^(@))/(v-v_(s) cos 45^(@)))`
`= 280 ((330+10// sqrt(2))/(330-20//sqrt(2)))`
`= 298 Hz`