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How could one explain the collision of two continuous mass distributions in view of

gravitation (Newtonanian and General relativity) ?

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What exactly is it that you want explained about the collision? –  David Z Nov 19 '10 at 5:35
@David Zaslavsky: I have asked in a cooment on Jerry Schrimer's answer. –  Rajesh D Nov 19 '10 at 6:08
I think you are all going too far with this black hole thing, my opinion is that he is just asking the different between the scattering of point-like particles and the scattering of spheres; this can be treated due to gravitational or electrostatic interactions (if the spheres are charged). No big deal with GR. Unless the question is very very strange ... –  Cedric H. Nov 20 '10 at 19:40
@Cedric H.: What do you think a black hole is ? a discontinuity in a mass distribution ? –  Rajesh D Nov 20 '10 at 19:52
@Rajesh: At first your question was not clear at all... I interpreted by "point mass" a geometrical point affected with a mass. A classical scattering problem like the one of a charged point-like particle. –  Cedric H. Nov 21 '10 at 10:58
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closed as not a real question by mbq, Sklivvz, Cedric H., Marek, Tobias Kienzler Nov 22 '10 at 8:20

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2 Answers

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In the context of classical mechanics, your question is probably ill-formed.

Since point masses have no physical extent, the gravitational force increases without bound as r approached zero, which it will indeed do because they'll only collide when they're superposed.

Infinite force on a finite mass implies infinite acceleration (F = ma) which implies infinite velocity, which is inconsistent with special relativity.

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In General Relativity, a point mass is a black hole. The collision of two black holes is a very complicated problem that has to be solved using numeric supercomputer simulation. The short story is that they end up coalescing to a single black hole.

There are some complications from this answer that could arise from spin-orbit coupling, but I don't think that's what you're asking about.

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Ok....i did'nt know that point masses are black holes. I was thinking that any system of particles as a system composed of point masses. Looks like in mechanics it seem to be a continuous distribution of mass. My question is what happens when two sperical distributions of mass collide ? Will they ? Even befor that how would a spherical(any shape) distribution of mass exist in view of gravity ? –  Rajesh D Nov 19 '10 at 6:07
depending on your answer i would want to ask more questions. –  Rajesh D Nov 19 '10 at 6:17
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