Subject: Center of mass within a two dimentional system

If I wanted to find the center of mass of a 
water molecule (H2O): each H = 1.0u  O = 16U. The 
hydrogen atoms are 0.96A from the oxygen (1A = 1 X 
10^-10 m) and are seperated by an angle of 105¤. (¤= degrees)

 H             H  _
  \           /    |
   \   105¤  /     |
    \-------/      | D = .96A
     \     /       |
      \   /        |
       \ /         |
        O         -

Re: Center of mass within a two dimentional system