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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: sci.physics.research
Subject: Re: Inertia and third principle
Date: Sun, 04 Aug 2024 07:53:54 PDT
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Approved: Jonathan Thornburg [remove -color to reply]" <dr.j.thornburg@gmail-pink.com (sci.physics.research)
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> Luigi Fortunati il 30/07/2024 19:05:34 ha scritto:
>>> In my animation https://www.geogebra.org/m/qterew9m ...
>> If body A passes some momentum to body B, body B must politely return  
>> to body A the *same* momentum it received, no more and no less.
>> [[Mod. note -- Newton's laws say that (assuming that there are no 
>> external forces acting) the *total* momentum of the system remains 
>> constant.
> 
> Sure! The *total* momentum of the system remains (undoubtedly) 
> constant, this is established by the law of conservation of momentum 
> which I have never disputed.
> 
>> If we look at the momentum *changes* during the collision, we have   
>> p_A_after - p_A_before = 3.75 - 15 = -11.25 , while B's momentum change 
>> during the collision is   p_B_after - p_B_before = 2.25 - -9 = +11.25 
>> so the momentum *changes* are indeed precisely opposite. -- jt]]
> 
> Yes, even the *changes* in momentum during the collision are equal and 
> opposite, otherwise the law of conservation of momentum which I have 
> never disputed would not be correct.
> 
> My objection concerns something else, it concerns the equality between 
> action and reaction (the third principle).

The law of conservation of momentum is equivalent to lawes of inertia
and reaction together. If conseervation of momentum is violated without 
interaction the law of inertia is violated. If conservation of momentum
is violated in an interaction the law of reaction is violated.

-- 
Mikko