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CM to particle's CM problem

  1. Jul 29, 2008 #1
    hi there.

    I'm having some problems with Center Mass calculations... I have a CM moving at x axis with Vx, and it as a mass of M.

    Now, assume CM is made of n particles, but i only know their masses(all equal m), not their speed. My problem is how do i find their velocities? By Energy and momentum conservation,

    substituting V in second; as M=m*n(Mass of mass center is the sum of the masses of all particles) and simplifying

    And I'm stuck here. Even if i begin to assume something, like a random velocity of one particle, i can't get a algorithm that have physical meaning for solving this equation in order to [tex]v_{i}[/tex] for every i

    Can any1 tell me if there's a solution, or at least a clue about it?

    Thanks in advance,
  2. jcsd
  3. Jul 29, 2008 #2

    Doc Al

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    Staff: Mentor

    You mean: You have a system with total mass M whose CM has a velocity = Vx.

    Not enough information.
    This is correct (by definition of CM).
    This is not correct.

    Simple example: Imagine a gas of particles in a jar. Total momentum = 0, velocity of CM = 0, yet total KE of the particles does not equal zero.
  4. Jul 30, 2008 #3
    Yeah, you are right..xD i must then reformulate my problem...xD

    Tk U very much
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