Science students knows that the gravitational force of attraction between two objects is inversely proportinal to R*R(where R is the distance between them). But, if we have two concentric rings with different radii, there center of mass is is the same point. So, R=0 for them. Hence, the Gravitational forve of attarction should be infinite. But, in practice we can easily separate such rings. How/why?
2006-11-25 13:11:43 · 5 answers · asked by gp2much 2 in Science & Mathematics ➔ Physics
The center of mass is a mathematical approximation that physicists use to simplify the problem. Event if the 2 concentric rings have the same center of mass, their mass is actually distributed in the ring, and the mass of a given ring never occupies the same space as the mass of the other ring. So R is never actually =0 in this problem.
2006-11-25 13:16:57 · answer #1 · answered by F.G. 5 · 1⤊ 0⤋
The guy above me said most of it, but I want to add one thing. If the two rings are exactly concentric, and you look at the gravitational attraction between two pieces of the rings in line with each other, you'll see you can always find a gravitational attraction in the opposite direction cancelling the force.
2006-11-25 13:26:19 · answer #2 · answered by Edgar Greenberg 5 · 1⤊ 0⤋
Please, near-death experiences have been properly researched by now. You kooks need to upgrade your choice of literature. When the body dies, the brain goes into oxygen starvation mode. No new blood means no new oxygen. At that point it will start hallucinating wildly. While the reason or mechanism behind this is a bit unclear it is not a bad way to go. At least your final moments will be trippy. You should ask any pilot who has done high-G training. Typically at very high Gs the blood can't reach the brain anymore and the pilots pass out. When they come to they describe the classic NDE experiences: tunnels of light, floating behind your body et al. But none of this will convince you, you want to cling to the belief that your pathetic human life is something greater, something eternal. Well, at least you won't know that it is not there.
2016-05-23 02:47:35 · answer #3 · answered by ? 4 · 0⤊ 0⤋
FG sums it up nicely. The equation for gravitational force assumes point masses (which don't actually exist anywhere in the universe). You need to start using integral calculus to describe the force between concentric rings (YUK!!).
2006-11-25 13:30:32 · answer #4 · answered by Mez 6 · 1⤊ 0⤋
The shell theorem (see reference) does the calculus for you for certain simple, spherically symmetric situations. When you simplify a problem like this to equivalent point masses, you need to take care that the simplifications are actually relevant to the situation at hand.
2006-11-25 14:32:15 · answer #5 · answered by Frank N 7 · 1⤊ 0⤋