Re: interesting math problem

Claudio Lapilli wrote:
> We are not necessarily expelling anything, this could be a particle
> accelerator (electromagnetic forces), or even a simple car (a very fast
> one) fueled by direct mass-energy conversion. If you consider a
> reaction propulsion by expelling gases, then you conserve momentum but
> that's one special case. In general, change in momentum is not zero but
> equals the external forces. Unless you know (or define) the external
> forces, this equation won't help you (one more equation but one more
> unknown variable). I understood from the OP formulation that he wasn't
> expelling anything since he didn't consider any mass lost in expelled
> gases. In such case, his formulation of the problem seems ok but he
> needs another equation. A mass conversion rate equation will probably
> make the problem simpler to solve. That's what I meant in my original
> post, but with fewer words.

I can only reiterate what I said: The problem, as stated, is
incosistent. What external forces are we talking about? He is
converting mass into kinetic energy, where did you see an external
force? Even if he defined dm=const*dt (where const=rate of conversion
of mass into energy) it's still incosistent because momentum isn't
conserved. I'm not trying to be pedantic, but this is a situation that
is incosistent with the equations involved in relativistic mechanics,
so can't be answered within it. As for an accelerating car, momentum is
still conserved (earth accelerates in the opposite sense). As for
electromagnetic forces in particle accelerators, electromagnetic fields
carry both linear and angular momentum.


>
> > What expanded postulate of relativity do you have in mind?
>
> I don't even think we have a technical disagreement at all. All
> concepts are clear in my opinion, we are simply proposing two different
> paths to arrive to a solution. Apparently, you don't read my posts
> thoroughly enough to understand my ideas or even my jokes. Whatever,
> I'm done with this thread.

OK, I put the {} (curly brackets) in the wrong place when I read this
(it was late). But your generalisation of my misreading of your joke is
wrong: I did read your post and disagree with it. Specifying a rate of
conversion of mass into kinetic energy won't solve anything. Feel free
to disagree, but, in areas like physics, objective truth exists.

.

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