1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    User Avatar

    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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook