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That is what I thought. Just confirming it. So then particles with mass have the relationship which cannot be true for massless particles traveling with a set velocity.So then we should be able to say since then kinetic energy can be expressed as . This will then reduce to . If I am wrong I would like to know.

It is interesting to consider that when c=G=1 then 2m describes the radius of the event horizon of a black hole.

Quote from: jeffreyH on 03/10/2015 16:24:21That is what I thought. Just confirming it. So then particles with mass have the relationship which cannot be true for massless particles traveling with a set velocity.So then we should be able to say since then kinetic energy can be expressed as . This will then reduce to . If I am wrong I would like to know.This algebra looks correct to me. is true for light, but it just reduces to 1 = 1, so it's just not a useful expression on its own. You can't get from there to the v of a massless particle, but the rest of the math works just fine for particles with mass.Quote from: jeffreyH on 03/10/2015 16:24:21It is interesting to consider that when c=G=1 then 2m describes the radius of the event horizon of a black hole.I don't know what c and G mean here, they are not mentioned previously in this post.

Can the relationship apply to all particles? If so then does still represent mv?

I believe the relationship holds for all particles. ρ = mv for all particles except for a photon, for which mv doesn't make any sense...

If you're speaking about mass defined as proper mass then you're [ RIGHT??? ]. However, if you were speaking about mass as the more useful concept relativistic mass (RM) then you'd be quite wrong. ...However, in my opinion, you should have made it clear to Jeff which mass you had in mind....

Quote from: PmbPhy on 08/10/2015 16:19:59If you're speaking about mass defined as proper mass then you're [ RIGHT??? ]. However, if you were speaking about mass as the more useful concept relativistic mass (RM) then you'd be quite wrong. ...However, in my opinion, you should have made it clear to Jeff which mass you had in mind....I mean proper mass. I rarely have to address relativistic mass, so my default has always been proper mass. I will always specify "relativistic" if that is what I mean. I suppose that for someone who constantly has to consider relativity, the opposite would be true, and proper mass would need to be specified, while relativistic mass would make a reasonable default...

Jeff: If you really want to read an article which makes all of this quite clear then you can read the article I wrote. It was published in an Indian Journal and is now in a book too. It's online at:...sorry, you cannot view external links. To see them, please REGISTER or LOGIN