Doppler effect when moving towards then past each other

PHolloway27
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You are driving along a highway at 27.50 m/s when you hear the siren of an emergency vehicle traveling in the opposite direction on the other side of the highway. When the vehicle is approaching you, you hear the frequency of the siren as 2800 Hz, but when it is past you the frequency becomes 2120 Hz. What is the speed of the emergency vehicle? The speed of sound in air is 340.0 m/s.
 
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Hi PHolloway27! Welcome to PF! :wink:

Show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
 
Seems like classic doppler to me

F2=F1(vsound/(vsound+/-vobject)

+ recceding
- approaching

just plug in the right numbers
 
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