An ambulance has f=400Hz as it goes away from you and 500Hz as it approaches you.

a) How fast is the ambulance going? I got 38.1m/s
[(500-400)/(500+400)]*343
b) What would be the frequency of an ambulance if it was not moving? I'm not sure how to get this.

Question

An ambulance has f=400Hz as it goes away from you and 500Hz as it approaches you.

a) How fast is the ambulance going? I got 38.1m/s
[(500-400)/(500+400)]*343
b) What would be the frequency of an ambulance if it was not moving? I'm not sure how to get this.

anonymous · Answer

Just use the basic equation for the doppler effect with moving source - plug in the value of ambulance speed and rearrange to get the 'normal' frequency of the ambulance siren.