Re: Is F=ma a definition or not?

From: Franz Heymann (notfranz.heymann_at_btopenworld.com)
Date: 01/14/05 

Date: Fri, 14 Jan 2005 17:45:53 +0000 (UTC)

"Mike" <eleatis@yahoo.gr> wrote in message
news:1105655325.489654.190670@f14g2000cwb.googlegroups.com...
>
> Franz Heymann wrote:
>
> [snip]
> >
> > He would, of course have been wrong, as the concept of "force" is
not
> > of much use in QM.
>
> Even classical mechanics can be formulated without the concept of
force
> used explicitely. But implicitely, and this is the point, without
the
> concept of virtual work there is not a ground of the laws of physics
> and the derivation of the Hamiltonian. The Hamiltonian must be
accepted
> as a a priori principle. How does that sound to you?

It sounds as if it is irrelevant to what has been discussed so far.
>
> >
> > Nevertheless, here is the space for the proof that Newton was
smart
> > enough to assume what you stated above.
> >
> > As counyter example, I remind you of the crap Newton spoke about
> > particles of light "suffering fits of easy transmission and firts
of
> > easy reflection"
>
> Optiks was a failure.

Most of it was.

> > The planets with elliptical orbits do not move at relativistic
> speeds.
> > Neither do the electrons in the ground state of atomic hydrogen
> >
>
> What do you imply? That F=dp/dt does not apply in elliptical orbits?

Newton's laws actually do not apply in the case of any planetary
orbits. It is only in the case of the elliptical orbits that the
deviation from Newtonian orbits can be observed.
>
> I will ask you the question I asked before Tom Roberts and he hide
> away.
>
> Can you state the equations of motion of a simple mass-spring-damper
> system in GR?

No, I can not. However, I do know that in the weak limit, GR and
Newton make the same predictions.

> His answer was that those equations are exactly what is
> derived by using F =dp/dt in classical mechanics because of the
> limiting solution of the GR equations:)

That's what I, also, said just above here.
It is correct.

> Even when using the Lagrangian formulation, it comes down to
> essentially F =dp/dt. The time derivative of the partial derivative
of
> L wrt to the generalized coordinate time rate of change is what is
> called a force F. So is the partial derivative of the potential
> function U wrt to the generalized coordinate:)

You're just bragging now.
>
> Remember: force is the only foundation of physics around,

No.
> even of
> relativistic physics and QM, although it may not appear explicitely
in
> the equations used. No force, no motion, period.

Bollocks. What happened to Newton's first law?

[snip]

Franz

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