# Speed of Sound and Doppler Effect

The speed of sound in air is about 660miles/hour. A passenger train approaches an unguarded railroad crossing at a constant speed of 60 miles/hour and the locomotive sounds its horn which has a frequency of 400 Hz.

[A]. What frequency does a listener standing near the crossing hear?

[B]. If the train continues past the crossing at the same speed, what frequency does the listener hear?

[C]. What frequency does a person riding on top of the last car hear? Why?

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#### Solution Preview

Speed of Sound = S = 660 miles/hr

Speed of Train (Source) = Vs = 60 miles/hr

Speed of observer = Vo = 0 miles/hr (A Stationary observer)

Frequency of Train horn (Source) = Fs = 400 Hz.

Determine Frequency heard by observer = Fo = to be determined for the three cases.

Equation: Fo = Fs * ...

#### Solution Summary

This solution explores the concept of the Doppler effect by determining the frequency of the observer standing near the crossing, when the train is at constant speed, and when the observer is on top of the last car. All steps and workings are shown with brief explanations.