`(n - 1)` equal point masses each of mass `m` are placed at the vertices of a angular n-polygon. The vacant vertex has `a` position vector `a` with respect to the centre of the polygon. Find the position vector of centre of mass.

Explanation

Let B be the position vector of the mass of a regular n- polygon , therefore for its centre of mass
`f_(CM)=((n-1)mb+ma)/((n-1)m+m)=0( :' "Centre of mass lies ata centre")`
`implies (n-1)mb+ma=0`
`impliesb=-(a)/((n-1))`