Manoj,
Well, briefly, the actual calculation involves a triple integral summation of density dxdydz. However, that may not be what you really are asking.
Think of parent and child on a see-saw. Dad's cg is in the middle of his body, say 4 feet from the pivot; his daughter's cg is on the other side, say 6 feet
from the pivot. The average of these two cg locations is 1 foot from the pivot on the daughter's side, but, obviously, the combined cg is not there but at the pivot itself, distance zero.
Not to confuse the issue, but, technically, what is being calculated by the software is center of mass, not center of gravity. In a gravitational field they are
not identical because the mass which is "lower" in the field has a greater effect. Thus the moon's center of gravity is closer to earth than its center of mass.
But that's just gratuitous nerdiness for the sake of completeness; we don't have a gravitational field at play within the ProE modeling environment, so center of mass and center of gravity are coincident.
David
