The Doppler Effect Homework: Speed of Train from 940Hz to 915Hz

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SUMMARY

The discussion focuses on calculating the speed of a train using the Doppler Effect, where a stationary observer hears a frequency change from 940Hz to 915Hz as the train passes. The speed of sound in air is established at 343 m/s. The formula used is Vs = ((Fs/Fo) - 1) * V, where Fs is the frequency heard by the observer, Fo is the original frequency, and Vs is the speed of the source. Participants report incorrect calculations, with one user consistently arriving at 9.4 m/s, which does not match the provided multiple-choice answers.

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Homework Statement


A train moving at a constant speed is passing a stationary observer on a platform. A flute player is playing a note with a frequency of 940Hz. after the flute has passed, the observer hears the sound frequency of 915Hz. What is the speed of the train? The speed of sound in air is 343m/s.

Homework Equations



Fo = Fs (1/(1+(Vs/V))

The Attempt at a Solution



Vs = ((Fs/Fo) - 1) * V

When i input the given information I keep getting the wrong answer. Is my arithmetic wrong or am I missing something completely?
 
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What is the given answer and what are you getting?
 
A) 7.3 m/s
B) 12 m/s
C) 21 m/s
D) 32 m/s
E) 42 m/s

I get 9.4 m/s
 
Same here unfortunately.
 

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