[Phys-L] Re: Energy is primary and fundamental?

[jeglin at 4PI.COM (Stefan Jeglinski)]

>  > 2. A criticism leveled at the classical mechanics version of the
> >  Principle is that although it can used to derive Newton's Laws (or at
> >  least the 2nd one), one needs Newton's Laws to do so.
>
> This is not an accurate criticism.   You can rigorously derive all
> of classical mechanics from PoLA.

In the on-line book you cite, I refer to section 1.6: How to Find Lagrangians:

"The key idea is to construct a Lagrangian L such that Lagrange's
equations are Newton's equations  F = ma."

This would seem to be one of my points: "we have to write it this way
to get the answer we want."

I'm not saying you can't rigorously derive all of classical mechanics
from PoLA, because your suggestions for study are not something that
I con do quickly. But I'm not seeing how the criticism is not
accurate, at least for the reference you cited.


Stefan Jeglinski