A police in a siren car moving with a velocity 20 ms^(-1) chases a thief who is moving in a car with a velocity v_(0)ms^(-1).The police car sounds at frequency 300 Hz, andboth of them move towards a stationary siren of frequency 400 Hz. Calculate the speed in whichthief is moving.

A police in a siren car moving with a velocity 20 ms^(-1) chases a thi

1.	A police in a siren car moving with a velocity 20 ms^(-1) chases a thief who is moving in a car with a velocity v_(0)ms^(-1).The police car sounds at frequency 300 Hz, andboth of them move towards a stationary siren of frequency 400 Hz. Calculate the speed in whichthief is moving.
Answer» Solution :Velocity of sound `V=330 m//s` Velocity of a police siren CAR `v_(s)=20 m//s` Frequency of a police siren car `f=300 Hz` Let the velocity of their be v m/s. Frequency of police siren heard by THIEF is `f_(1)=((330-v)/(330/20))xx300` `=((330-v)/(310))xx300HZ` Frequency of stationary sire `=400 HZ` Freqeuncy of stationary siren heard by thief `f_(2)=((330+v)/(330))xx400` It there are no beats then `f_(1)=f_(2)` `((330-v)/(310))xx300=((330+v)/(330))xx400` `(330-v)xx0.9677=(330+v)xx 1.2121` `330xx0.2444=2.7198v` `:.v=(0.2444xx330)/(2.1798)` `=36.99` `=37 m`