Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Finding centre of mass

  1. Jan 6, 2008 #1
    hi,
    Can anyone please help me to find the centre of mass of an object in a 3D co-ordinate system.
    Thanks in advance
     
  2. jcsd
  3. Jan 6, 2008 #2

    Shooting Star

    User Avatar
    Homework Helper

    In cartesian co-ordinates, the CM of of a system of particles is [sigma miri]/total mass. Simply put, multiply the mass at a point by its posn vector, add all of these, and divide by the total mass.

    If it's a continuous distribution, it will become triple integral [r*rho(r)dV]/total mass, where rho(r) is the density at r.

    EDIT: This is the general form, not limited to Cartesian co-ordinates.
     
    Last edited: Jan 6, 2008
  4. Jan 6, 2008 #3
    can u plz wht does the r stands for?
     
  5. Jan 6, 2008 #4

    Shooting Star

    User Avatar
    Homework Helper

    r denotes the position vector of a point wrt the origin. For example, if the Cartesian co-ordinates of a point is (x,y,z), then r = xi + yj + zk.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook