Question

A Loyola bus going southbound at 25.0 m/s on Lake Shore Drive (LSD) near the Irving Park exit, notices CPD behind them with lights flashing and siren blaring. The police are going 40.0 m/s and are using a siren that operates at f = 1000.0 Hz. Assume the speed of sound at this stretch of LSD is 340.0 m/s. The bus driver pulls over to stop while CPD continues past without changing speed. QUESTION calls for two frequencies: What frequency did the bus passengers hear when the bus was in front of the police car, and after they have stopped?

Answer 1

Observed frequency v is given as v=U + Uo Vo U-Us Vo actual prequency, a speed of sound Uo → Speed of obserwer W.y.t the medium, considered 1 tue, when it moves towards the innee. and ave when it mores away from the source Us speed of source World, the medium considered the when it moves towards the observer and we when it mores away from the observer, No=1000 Hz Uo=-25 mls (moving away from severce.) Us = 40mis (moving towards the observer) 2 = 340~25 x1050 340-40 =1050HZ when both stopped. & Us = 40=0 9 ) 2 2 = 165 12