Understanding Lagrangian Action: Tips from a Student

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Discussion Overview

The discussion centers around the concept of action in classical mechanics, specifically its definition and physical meaning as understood through the lens of the Lagrangian formulation. The scope includes theoretical explanations and personal reflections on learning the topic.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Ray Veldkamp expresses confusion about the definition of action, noting it is defined as the integral of the Lagrangian with respect to time.
  • Marlon provides a link to an external resource on the action principle, suggesting it as a reference for further understanding.
  • Daniel asserts that action is an essential functional in theoretical physics and reiterates that it is the integral of the Lagrangian over time, emphasizing the extremum principle as fundamental in nature.
  • AM shares a similar confusion about the physical meaning of action and recommends Feynman's lectures as a resource for better understanding.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the concept of action, with no consensus on its physical interpretation. Some provide resources while others share personal struggles with the topic.

Contextual Notes

The discussion highlights the challenge of grasping the physical meaning of action, indicating that while the mathematical definition is clear, its implications in physics may require deeper exploration.

Who May Find This Useful

Students beginning their studies in classical mechanics or those interested in the Lagrangian formulation may find this discussion relevant.

rayveldkamp
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Hi, I've just started a course in Classical Mechanics, in 3rd year undergraduate physics, and I'm a bit confused as to what exactly an ACTION is.
All we've been told is that the action, S is defined as the integral from t1 to t2 of the Lagrangian with respect to time.
Thanks in advance

Ray Veldkamp
 
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Thanks for the help, I'm sure I'll have plenty more Classical mechanics questions this semester
 
It is the essential functional in all theoretical physics...For discrete systems,it is indeed the integral of the function called LAGRANGIAN wrt time between specifed fixed limits.

Daniel.

Adn the extremum principle joining it is the fundamental principle in nature.
 
rayveldkamp said:
Hi, I've just started a course in Classical Mechanics, in 3rd year undergraduate physics, and I'm a bit confused as to what exactly an ACTION is.
All we've been told is that the action, S is defined as the integral from t1 to t2 of the Lagrangian with respect to time.
The action is easy enough to define mathematically but its physical meaning is a very difficult thing to understand. I struggle with it. I would highly recommend Feynman's lecture - Chapter 19 in Volume II of The Feynman Lectures on Physics.

AM
 

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