Understanding Generalized Coordinates in Goldstein's Classical Mechanics

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Discussion Overview

The discussion revolves around the concept of generalized coordinates as presented in Goldstein's classical mechanics. Participants explore the nature of generalized coordinates, particularly in relation to polar and spherical coordinates, and whether all coordinate systems can be classified as generalized coordinates.

Discussion Character

  • Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants propose that polar and spherical coordinates can be considered generalized coordinates, suggesting that any coordinate system different from Cartesian can be classified as such.
  • Others argue against this view, emphasizing that generalized coordinates are not limited to non-Cartesian systems and questioning the definition of generalized coordinates in the context of one-dimensional movement.
  • A participant asserts that generalized coordinates encompass any coordinate system, including Cartesian, spherical, and cylindrical, and that one can choose any convenient coordinate system for solving problems using Lagrange's equations.
  • Another participant agrees that polar and spherical coordinates are generalized coordinates for a single particle's position but notes that generalized coordinates are broader and include Cartesian coordinates as well.

Areas of Agreement / Disagreement

Contextual Notes

Participants highlight the ambiguity in defining generalized coordinates and the implications of different coordinate systems on problem-solving in classical mechanics, but do not resolve these issues.

radou
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I have just started to read Goldstein's classical mechanics, and he got me a bit confused: is it correct to think of polar and spherical coordinates as of generalized coordinates? the way I got it, every coordinate system different from the standard cartesian-one is a set of generalized coordinates...?
 
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No. Think about the 1D movement along the "x" axis. Which is the generalized coordinate...?

Daniel.
 
Generalized coordinates refer to any coordinate system. i.e. a statement about generalized coordinates holds for cartesian, spherical, cylindrical, etc. coordinate systems. In particular, one is free to choose any convenient coordinate system for a problem and solve the problem using Lagrange's equations for that coordinate system.
 
radou said:
I have just started to read Goldstein's classical mechanics, and he got me a bit confused: is it correct to think of polar and spherical coordinates as of generalized coordinates?

Yes, polar and spherical coordinates are generalized coordiantes for the position of a single particle. But general coordinates are a lot moe general. And cartesian coordinates are, technically at least, also "general coordinates".

Carl
 

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