On Saturday, January 12, 2019 at 6:21:49 PM UTC+2, Phillip Helbig (undress to
reply) wrote:
> In article , Luigi Fortunati
> writes:
>
> > The second principle says that F=m*a and F1=m1*a1. (1)
>
> Yes. I can call them what I want. F_george=mass_george*a_george.
>
> > The third principle says that for every action F corresponds an equal
> > and opposite F1 reaction, ie an F1 such that F1=-F. (2)
>
> Right.
>
> > Substituting the (2) to (1) we have F=m*a and -F=m1*a1.
>
> OK.
>
> > Adding the first and second members we have: F-F=(m*a)+(m1*a1), from
> > which the corollary: m*a=-(m1*a1) in which there are no forces but only
> > equivalences between different masses with different accelerations.
>
> You can't just add them. The third principle says that for a specific,
> given, F, there exists -F. You can't just add this to the general
> definition. It "works" only because you wrote "F1 such that F1=-F". In
> other words, you chose to call it F1. Why? I could say "F2 such that
> F2=-F" which is just as valid since now we are considering only the
> third principle, but then the addition trick doesn't work.
========================
we have in collision cases
two
kinds of collision :
for instance
I sit on a chair
I remain steady on my place
the same with the chair
ie
a ''static'' collision case
2
a dynamic collision case :
I throw a ball to the ground
the ball is jumping to **back/opposite direction**
and earth ..???
even earth is ''jumping back'' ..
but so small that it is negligible *** practically**
iow (in other words )
we have to examine
each case to itself
now something else:
In an absolute **elastic collision**
there is no loss of energy !!!!
============================
TIA
============
Eng
Y.Porat
===========
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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