Speed of sound, frames of reference

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Homework Help Overview

The discussion revolves around the speed of sound in different frames of reference, specifically in relation to three moving points labeled A, B, and C. The original poster presents their understanding of how the speed of sound should be calculated relative to these points.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to calculate the speed of sound relative to stationary and moving reference points, leading to questions about how motion affects perceived speed. Some participants explore the implications of relative motion on the speed of sound as perceived by different observers.

Discussion Status

Participants are actively engaging with the original poster's calculations and reasoning. There is a back-and-forth dialogue where some participants affirm the original poster's understanding while others prompt further exploration of the concepts involved.

Contextual Notes

There is a lack of explicit equations provided for the calculations, and the original poster acknowledges errors in their initial answers, prompting a request for clarification and guidance.

saccapella
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Homework Statement



[PLAIN]http://www.antonine-education.co.uk/Physics%20A%20level/Options/Module_8/Topic_6/cars_4.gif

What is the speed of sound, relative to:
A -
B -
C -

Homework Equations



None.

The Attempt at a Solution



For B, since B is a stationary reference point, the speed of sound relative to B should 330ms^-1

For A, I thought it should be 360, since A is a moving reference in the same direction as the speed of sound. Meaning A = 330+30=360

For C, I thought it should be 300, since the moving reference is moving in the opposite direction to the speed of sound, making B=330-30=300

My answers for A and C are wrong, however. Help!
 
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Imagine that the sound is represented by a runner going at some velocity v. From A's point of view, will the runner be moving more quickly or more slowly?
 
Slowly, right...?
 
saccapella said:
Slowly, right...?

Right... so... what will be the speed of sound as "seen" by car A?
 
300?
 
saccapella said:
300?

Yup.

Now figure out what speed car C "sees".
 
360...? Because the sound is towards C so the speed will 'seem' faster?
 
I think you understand it well enough now to answer your own question :wink:
 
Lol you're right on that :)
 

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