A car moving at `108 km h^-1` finds another car in front of it going in the same direction at `72 km h^-1`. The first car sounds a horn that has a dominant frequency of 800 Hz. What will be the apparent frequency heard by the driver in the front car ? Speed of sound in air ` = 330 ms^-1`

Explanation

`{:(rarr v_(s),,rarr v_(o)),(overset(*)(S),,overset(*)(O)),(,rarrv,):}`
`v_(s) = 108 km//hr = 108 xx (5)/(18) = 30 m//s`
`v_(o) = 72 km//hr = 72 xx (5)/(18) = 20 m//s`
`v = 330 m//s`
`f = 800 Hz, f' = ?`
`f' = f((v - v_(0))/(v - v_(s)))`
`= 800((330 - 20)/(330 - 30)) = 827 Hz`