Hamiltons Principle proving Newtons laws?

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Discussion Overview

The discussion revolves around Hamilton's principle and its relationship to Newton's equations of motion, particularly in the context of proving the validity of Newton's laws for multiple particles. Participants explore the necessity and implications of using generalized coordinates in this framework.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses uncertainty about the need for generalized coordinates in Hamilton's principle and seeks clarification on its significance.
  • Another participant highlights that the use of generalized coordinates can leverage symmetries in the system to recover Newton's equations, suggesting that rectangular coordinates associated with Euclidean space are a suitable choice.
  • A clarification is made regarding Hamilton's principle, emphasizing that it pertains to the action integral of the Lagrangian being stationary along the path of a particle.
  • Discussion includes the description of configuration space and the relationship between tangent-bundles and cotangent-bundles in the context of Hamiltonian and Lagrangian formulations.
  • One participant acknowledges difficulty in understanding the concept of changing perspectives on space, indicating a struggle with the abstract nature of the topic.

Areas of Agreement / Disagreement

Participants exhibit varying levels of understanding and clarity regarding Hamilton's principle and its implications for Newton's laws. There is no consensus on the necessity of generalized coordinates or the conceptual framework surrounding them, indicating ongoing exploration and differing interpretations.

Contextual Notes

Participants express uncertainty about specific definitions and concepts, such as the nature of configuration space and the implications of using generalized coordinates. There are unresolved questions regarding the relationship between Hamilton's principle and the geometric interpretations of the formulations discussed.

Who May Find This Useful

This discussion may be of interest to students and educators in physics, particularly those exploring classical mechanics, Lagrangian and Hamiltonian formulations, and the foundational principles underlying motion and dynamics.

frenchyc
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My teacher asked us too prove that Hamiltons principle proves that Newtons equations of motion hold for N particles. I'm not sure that i fully grasp the concept but this is my understanding so far:

Using the lagrangian we can prove Newtons law for specific situations, however Hamiltons principle allows us to make the specific situation into generalized coordintes. This is my understanding so far, but i feel that i don't completely understand. Why do we need it to be in generalized coordinates? Why does hamiltons principle allow it to change to generalized coordinates?
 
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One of the strengths of the Lagrangian and Hamiltonian formulations is the ability to use generalized coordinates, which can often be chosen to take advantage of symmetries in the system. To recover Newton's equations, you should choose the generalized coordinates to be the rectangular coordinates associated with Euclidean space.

The above formulations can be given a geometrical interpretation in which the "space" associated with the Lagrangian formulation is a certain manifold called the tangent-bundle and the Hamiltonian formulation with the cotangent-bundle (more generally, a symplectic manifold).
 
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I'm sorry but i was not referring to the Hamiltonian, but to Hamilton's principle. The principle that states that the path that a particle follows is such that the action integral of the Lagrangian from point 1 to point 2 is stationary. I am not sure if you were referring to that and i simply didn't understand it or if there was a miscommunication
 
the configuration of the system is described using a "configuration space" Q (which could be described in any convenient set of coordinates for it)
the tangent-bundle is essentially the "space of configurations and velocities" (TQ)
the cotangent-bundle is essentially the "space of configurations and momenta" (T*Q)

possibly useful:
http://books.google.com/books?id=I2...P79&sig=UrhQn9eZ_avFCBudNiPHYVjRjIM#PPA226,M1
 
thank you. I think my problem stems from me having difficulty wrapping my mind around this concept of changing the way we look at space.
 

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