Groups > sci.physics.relativity > #476391

Re: Relative motion again

From	Sylvia Else <sylvia@email.invalid>
Newsgroups	sci.physics.relativity
Subject	Re: Relative motion again
Date	2018-11-06 18:10 +1100
Message-ID	<g4ct3lF90mbU1@mid.individual.net> (permalink)
References	<5a7ad418-fc96-4c4c-b352-140904aeed03@googlegroups.com> <g4cbr4F5gouU1@mid.individual.net> <21c231c1-6dad-41e1-84d3-ba79f3ce0516@googlegroups.com>

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On 6/11/2018 2:58 pm, xip1415926@gmail.com wrote:
> On Monday, November 5, 2018 at 9:16:07 PM UTC-5, Sylvia Else wrote:
> 
>> This is wrong. You are making the unfounded assumption that velocities
>> combine by addition, when they do not. The difference is negligible for
>> small velocities, but large when the magnitudes of the velocities
>> approach the speed of light.
>>
>> Sylvia.
> 
> You are talking about relativistic addition of velocities:
> 
> v = [ a + b ] / [ 1 + ( a · b ) / c² ]
> 
> When a and b are each approximately equal to c you have:
> 
> v = [ c + c ] / 2 = c
> 
> The problem at hand has nothing to do with this.  Problem:  In a junior high school science class, under what circumstances does v exist at all ???  As I pointed out v = a + b exists only for the teacher at the blackboard and does not normally exist for walkers A and B separately.
> 

You've heard of it, but you don't apply it, as is apparent when you try 
to get c + v being the velocity of light send by an observer.

Sylvia.

Thread

Relative motion again xip1415926@gmail.com - 2018-11-05 10:49 -0800
  Re:Relative motion again Libor Striz <poutnik4REMOVEnntp@CAPITALSgmail.com> - 2018-11-05 20:16 +0100
    Re:Relative motion again Buck Dehner <uktea@yswdoiz.cp> - 2018-11-05 21:07 +0000
      Re:Relative motion again Libor Striz <poutnik4REMOVEnntp@CAPITALSgmail.com> - 2018-11-05 22:55 +0100
        Re:Relative motion again Buck Dehner <uktea@yswdoiz.cp> - 2018-11-05 22:46 +0000
          Re:Relative motion again Libor Striz <poutnik4REMOVEnntp@CAPITALSgmail.com> - 2018-11-06 01:22 +0100
            Re:Relative motion again Ntowicz Usarczyk <iswso@wioioksi.io> - 2018-11-06 20:27 +0000
  Re: Relative motion again Sylvia Else <sylvia@email.invalid> - 2018-11-06 13:16 +1100
    Re: Relative motion again benj <benj.fake@gmail.com> - 2018-11-05 21:45 -0500
      Re: Relative motion again Sylvia Else <sylvia@email.invalid> - 2018-11-06 14:57 +1100
    Re: Relative motion again xip1415926@gmail.com - 2018-11-05 19:58 -0800
      Re: Relative motion again xip1415926@gmail.com - 2018-11-05 21:24 -0800
      Re: Relative motion again Sylvia Else <sylvia@email.invalid> - 2018-11-06 18:10 +1100
      Re: Relative motion again Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-11-06 09:21 +0100
        Re: Relative motion again xip1415926@gmail.com - 2018-11-06 06:03 -0800
          Re: Relative motion again Tom Roberts <tjroberts137@sbcglobal.net> - 2018-11-06 08:41 -0600
            Re: Relative motion again Ntowicz Usarczyk <iswso@wioioksi.io> - 2018-11-06 20:32 +0000
              Re: Relative motion again Tom Roberts <tjroberts137@sbcglobal.net> - 2018-11-06 20:39 -0600
                Re: Relative motion again Ntowicz Usarczyk <iswso@wioioksi.io> - 2018-11-07 19:44 +0000
          Re: Relative motion again Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-11-06 22:32 +0100

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