Galilean Transformation Question

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Discussion Overview

The discussion centers around the Galilean transformation, specifically the equations governing the relationship between two reference frames, S and S', where S is at rest and S' is moving in the positive x direction. Participants explore the reasoning behind the equation for the x-coordinate transformation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the Galilean transformation for the x-coordinate is given by x' = x - vt instead of x' = x + vt.
  • Another participant explains that since the origin of S' moves towards the object on the positive x-axis, the x' coordinate decreases over time, supporting the equation x' = x - vt.
  • A further contribution clarifies that in the S frame, an object moving with the origin of S' has coordinates (x, t) = (vt, t), while in the S' frame, the coordinates are (x', t) = (0, t), indicating that using x' = x + vt leads to incorrect results.
  • One participant expresses gratitude for the clarification and acknowledges their self-taught background.
  • Another participant emphasizes the importance of understanding these concepts clearly, especially for future studies in special relativity (SR).

Areas of Agreement / Disagreement

Participants generally agree on the equation x' = x - vt as the correct form of the Galilean transformation for the x-coordinate, but there is an initial question regarding its derivation. The discussion reflects a mix of clarification and exploration of the topic.

Contextual Notes

Some assumptions about the motion of the frames and the initial conditions are not explicitly stated, which may affect the understanding of the transformation. The discussion does not resolve all potential ambiguities in the application of the transformation.

Who May Find This Useful

This discussion may be useful for students or individuals interested in classical mechanics, particularly those studying reference frames and transformations in physics.

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What happens if I have 2 frames,S and S', with S as my rest frame and S' moving in the +ve x direction (towards the right). Why is it that the equation for the galilean transformation for the x-coordinate is [tex]x'=x-vt[/tex] instead of [tex]x'=x+vt[/tex] ?
 
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Think of an object lying on the positive x-axis (it therefore also lies on the x'-axis). At t=0 the x and x' coordinate of the object are the same, but since the origin in S' moves towards the object (as seen from S. In S' the object moves towards the origin.) the x' coordinate decreases with time. So x'=x-vt is the right equation.

Drawing a picture also helps.
 
The primed coordinates are the coordinates measured by the "moving" frame. Take a simple case: Imagine an object moving along with the origin of S'. After a time t, the S frame says the object's coordinates are (x,t) = (vt,t). Of course, the S' frame gives the coordinates as (x', t) = (0, t). Using [itex]x'=x+vt[/itex] gives the wrong answer.
 
hey thanks a lot, I've gottit, sorry if my questions are a little too simple, I'm mostly self-taught.
 
There's no problem with us:it's essential for you to have these problems clear,especially if you want to go into studying SR,where things are a bit more difficult...

Daniel.
 

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