Solve Doppler Problems: Train & Person

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SUMMARY

The discussion focuses on solving a Doppler effect problem involving a train approaching an observer at a speed of 35.0 m/s while emitting a whistle at a frequency of 2.5 kHz. The correct formula to use is f' = f (v + vo) / (v - vs), where v represents the speed of sound in air, vo is the speed of the observer (zero in this case), and vs is the speed of the source (the train). As the train approaches, the frequency heard by the observer increases, while it decreases as the train recedes.

PREREQUISITES
  • Understanding of the Doppler effect
  • Familiarity with the formula f' = f (v ± vo) / (v ∓ vs)
  • Knowledge of sound wave properties
  • Basic algebra skills for manipulating equations
NEXT STEPS
  • Calculate the frequency heard by the observer as the train approaches using the Doppler effect formula.
  • Determine the frequency heard by the observer as the train recedes.
  • Research the speed of sound in air at different temperatures.
  • Explore real-world applications of the Doppler effect in various fields such as astronomy and radar technology.
USEFUL FOR

Students studying physics, educators teaching the Doppler effect, and anyone interested in understanding sound wave behavior in motion scenarios.

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Homework Statement


A train approaches an observer at 35.0 m/s and passes a person stading on the side of the track. The whistile is sounding at 2.5 kHz. What frequency will the person hear as the train approaches? When it recedes?

Homework Equations


f' = f \frac{v \pm v<sub>o</sub>}{v \mp v<sub>s</sub>}

The Attempt at a Solution


f' = 2500 Hz(?)

I don't know what number I should put into the equation.
 
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Yes, what a miserable formula that is!
It looks a little better here: http://en.wikipedia.org/wiki/Dopplar_Effect
(scroll down 1 screenfull)
Since the receiver is not moving, the formula is
f = fi*V/(V + Vs)
Here V is the speed of sound in air, and Vs is the speed of the source. The speed of the source toward the receiver increases the frequency, so you must make Vs a negative number (dividing by a smaller number makes the result larger).
 

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