the center of mass->

[deda]

This is attempt to address Arcon's page on
center of mass (http://www.geocities.com/physics_world/sr/center_of_mass.htm)

He says: \vec{R}=\frac{\sum m_i\vec{r_i}}{M}
R is radius vector of the center;
ri are radius vectors of mi;
M is sum of all mi;

It can be generalized to vector mass too.

M\vec{R}=M\vec{e_M}\times\vec{R}\times\vec{e_M}=\v ec{M}\times\vec{R}\times\vec{e_m};

also just like
\vec{M}=\sum \vec{m_i}
under special conditions it can as well be
\vec{R}=\sum \vec{r_i}

=> (\sum \vec{r_i})\times(\sum \vec{m_i})=\sum (\vec{r_i}\times\vec{m_i});

=> \sum_{i<>j} (\vec{r_i}\times\vec{m_j})=\vec{o};

This way the position of the last mass depends on all the masses (including its own) and all the other positions;

I just can't say what are the terms for the last equation.
Can you?