Doppler effect with moving source and observer

In summary, by using the equation fo=fs(1+- vo/v)/(1+-vs/v), we can determine that the ambulance was traveling at a speed of approximately 17.5 m/s when it passed the observer's vehicle. A second equation can also be used to solve for the ambulance's speed before and after passing the observer.
  • #1
hopelessphysics
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Homework Statement


As you drive at a speed of 15.0 m/s an ambulance approaches you from behind with its siren blaring at a frequency of 1022 Hz. After the ambulance has passed you the signal is now 981 Hz. If both you and the ambulance travel at a constant speed how fast was the ambulance traveling?

Homework Equations


fo=fs(1+- vo/v)/(1+-vs/v)

The Attempt at a Solution


So I tried to use the equation above by plugging in the frequencies, but was trapped because the frequencies show only what the source was emitting, and not what the observer was hearing.
 
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  • #2
fo is the observer frequency.
You don't have the source frequency, but you have a second equation you can use.
 
  • #3
What is the second equation?
 
  • #4
The ambulance before and after it passes you => 2 equations
 

1. What is the Doppler effect?

The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the source of the wave. It is commonly observed in sound waves, light waves, and other types of waves.

2. How does the Doppler effect work with a moving source and observer?

When a source of a wave is moving towards an observer, the wavelength of the wave appears to be shorter and the frequency appears to be higher. When the source is moving away from the observer, the wavelength appears to be longer and the frequency appears to be lower.

3. What is the difference between the Doppler effect for sound waves and light waves?

The Doppler effect for sound waves involves changes in the perceived pitch of the sound, while the Doppler effect for light waves involves changes in the perceived color or frequency of the light. Additionally, since sound waves travel at a much slower speed than light waves, the Doppler effect is more noticeable in sound waves.

4. How does the speed of the source and observer affect the Doppler effect?

The speed of the source and observer affects the magnitude of the Doppler effect. The faster the source is moving towards or away from the observer, the greater the change in frequency or wavelength will be. The speed of the wave itself also plays a role in the Doppler effect.

5. How is the Doppler effect used in real life?

The Doppler effect is used in many practical applications, such as radar and sonar systems, weather forecasting, and medical imaging. It is also used in astronomy to study the movement of stars and galaxies. In everyday life, the Doppler effect can be observed in the change in pitch of a siren as an ambulance or police car passes by.

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