Foundations: Newton's Third Law and time reversal invariance

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The discussion centers on the reformulation of classical dynamics principles for educational purposes, emphasizing the importance of time reversal invariance and its connection to energy conservation. Participants express skepticism about the necessity of Newton's Third Law as an independent principle, arguing that conservation of momentum inherently covers its implications. The conversation highlights the confusion novices face with the Third Law and suggests focusing on conservation laws instead. Additionally, there is a debate about the relevance of Lagrangian mechanics and Noether's theorem in understanding symmetries and conserved quantities in physics. The overall sentiment leans towards modernizing the teaching of classical dynamics to enhance comprehension.
  • #31


Shahin.Omar said:
When you start saying things like; 'good definition of exist or real', 'fictitious forces', 'pseudo forces', 'complicated nature of the issue', 'true vs apparent', 'ifs and buts'. Sorry to say, but they only mean one thing, you have failed to grasp it!

Imagine you are a judge, and there is a witness who uses phrases like the above, what impression would you get?

When you say 'it is complicated' what you really mean is 'it is complicated for me'. When it is complicated for you, tell me what would it be like for the kids, and this is the point here?

On the surface of Earth or inside an accelerated spaceship, you feel the same thing; your weight or gravitational mass' where is the complicacy? You start using terms like d'Alembert's force and it is bound to look complicated.
OK, since you have grasped the issue and it is so simple and you are so smart and I must be an idiot to have ever thought it was complicated please post your clear and easy definition of "exist" which can be applied to forces to show that the forces you listed do exist and inertial forces do not.
 
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  • #32
I think this thread has been thoroughly hijacked and gone off the deep end. If the OP has further questions, please contact me to reopen this thread.

Zz.
 

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