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A comment on Perpetual motion?. Parent comment

Re:Perpetual motion? by cool-RR on Thursday February 04, 2010 @07:17PM (#1102156)
It says "the total rest masses." This is talking about the rest mass, which is different than the relativistic mass. I believe that the relativistic mass is the one that actually matters.

To your question, I agree that the energy released would be Δmc², but there would be no conversion between mass and energy in the process. The total mass and the total kinetic energy would remain the same after the fission as they were before it.

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Re:Perpetual motion? by ericd on Thursday February 04, 2010 @07:42PM (#1102222)
Ah, so once the byproducts are again at rest with 0 kinetic energy, total mass of the system will be equal to total mass of the system before?

So the energy of the explosion comes purely from the atoms being at a lower energy state than they were as uranium? I suppose it makes sense if it takes a huge outlay of energy to form them, which stars could certainly source.

I should go watch some physics OCW...

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