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From: Luigi Fortunati <fortunati.luigi@gmail.com>
Newsgroups: sci.physics.research
Subject: Re: Newton's Third Law and Inertia
Date: 8 Apr 2025 16:01:02 GMT
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Mikko il 08/04/2025 10:27:48 ha scritto:
>> Newton, with his archaic language, when he wrote "force" meant force
>
> That does not make sense. In the midern language the word "force" has
> a wide variety of different meanings. It had most of these meanings
> already in 1729 when Motte translated Principia in English. However,
> one important meaning is newer: a quantity in physics. As Newton did
> not define the term before its use in the definition of "vis insita"
> it must be intepreted according to its meaning in ordinary English of
> the year 1729, or one must interprete the original Latin text according
> to the common Latin meanings of the year 1726 when the 3rd edition of
> Principia was published.

You are right that in modern language we have complicated the concept 
of "force" to give it a wide variety of different meanings, which did 
not exist in Newton's time.

But in the collision language of any year and any century it has a 
single and unequivocal meaning: force is the push that body A exerts on 
body B and, also, that which body B exerts on body A.

And why do bodies A and B, when they collide, push each other?

They do so exclusively because of their contrasting inertias: if the 
inertia of body A did not wanted to go to the right while the inertia 
of body B wants to go to the left, there would be no action and 
reaction forces.

In collisions, the opposing inertias of the two bodies are the cause 
and the action and reaction forces of the third law are the effects.

In Newton's time and also in our time.

Luigi Fortunati