An ambulance is traveling east at 60.7 m/s. Behind it there is a car traveling along the same direction at 32.3 m/s. The ambulance driver hears his siren at a frequency of 521 Hz.

Question

An ambulance is traveling east at 60.7 m/s. Behind it there is a car traveling along the same direction at 32.3 m/s. The ambulance driver hears his siren at a frequency of 521 Hz. 
At what frequency does the driver of the car hear the ambulance’s siren? The velocity of sound in air is 343 m/s. Answer in units of Hz

Henry · Answer

Fr = (Vs-Vc)/(Vs+Va)*Fa Fc = (343-32.3)/(343+60.7)*521 = 401 Hz= Freq. heard by car driver.

Mauricio · Answer

The sign on the numerator should be a positive not a negative because the car (receiver) is approaching the ambulance (emitter).