Two cars are approaching each other on a straight road and moving with a velocity of 60 kmph. If the sound produced in one car is of frequency 500 Hz, what will be the frequency of sound as heard by a person sitting in another car ? When the car has crossed and moving away from each other , what will be the frequency of sound as heard by the same period ? (speed of sound in air is `332 ms^(-1)` )

Explanation

Given `V_(0) = V_(S) = 60` kmph
i.e. `V_(0) = V_(S) = (60 xx 5)/(18) ms^(-1)`
i.e. `V_(0) = V_(S) = 16.67 ms^(-1) , V = 332 ms^(-1)`
Apparent frequency as heard by the observer moving towards the approaching car `f' = f ((V + V_(0))/(V - V_(S))) , f = 500`Hz.
i.e. , `f' = (500 xx (332 + 16.67))/((332 - 16.67))`
i.e. `f' = (500 xx 348. 67)/(315.33) = 552.86` Hz
When the two cars move away from each other `f' = f ((V- V_(0))/(V + V_(S)))`
i.e., `f' = (500 xx 315 .33)/(348.67) = 452.19` Hz.