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From: Luigi Fortunati <fortunati.luigi@gmail.com>
Newsgroups: sci.physics.research
Subject: Re: Gravitational mass and inertial mass
Date: 4 May 2024 09:50:12 GMT
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Il 19/04/2024 12:52, Luigi Fortunati ha scritto:
>>> In my animation https://www.geogebra.org/m/kqjzk5gt there are the two bodies A and B (of equal mass m) connected via an inextensible wire, ideally massless.
> The string AB receives the blue force FA=mg from body A
> and transmits it to point B of body B.
> 
> However, the black force -FB that the string transmits to body B is only
> half the force it received at point A.
> 
> What happened to the force that was lost? Where is the error in the
> animation or in the reasoning I did?

Since no one wanted (or knew) to answer me, I thought on my own and 
found the error in my animation https://www.geogebra.org/m/kqjzk5gt

I thought like this...

The system composed of the two bodies A and B and the string AB behaves 
like a single body because it accelerates in the same way at all its 
points, without exception.

There cannot be a point that accelerates and another point that does not 
accelerate.

And therefore, in the direction of acceleration the opposing forces (at 
each point) cannot be balanced, otherwise there would be no net force 
and there would be no acceleration.

Instead, the acceleration is there and the prevailing force must be there.

Take, for example, point B accelerating to the right.

 From the side of the string AB the black force comes to him which pulls 
him to the right, from the side of the body B the red force comes to him 
which pulls him to the left.

If the two opposing forces (black and red) were equal, point B would 
accelerate neither to the right nor to the left.

And since point B accelerates to the right, it means that the black 
force cannot be equal to the red force but must be *greater*!

And then, I created the new animation 
https://www.geogebra.org/m/zxt8ysv6 where the black and blue forces are 
equal to mg, and the red and brown forces are equal to mg/2).

How to reconcile my last animation (which is correct) with the third 
law, that of action and reaction?

Luigi Fortunati