$(n - 1)$ equal point masses each of mass $m$ are placed at the vertices of a regular $n-$ 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. 

A carpenter has constructed a toy as shown in the adjoining figure. If the density of the material of the sphere is $12$ times that of cone, the position of the centre of mass of the toy is given by

Define the position vector of centre of mass.

$A$ slender uniform rod of length $\lambda$ is balanced vertically at a point $P$ on a horizontal surface having some friction. If the top of the rod is displaced slightly to the right, the position of its centre of mass at the time when the rod becomes horizontal :

For determining centre of mass of a body why a body is considered as composited of multiple of small mass elements ? 

Figure shows a composite system of two uniform rods of lengths as indicated. Then the coordinates of the centre of mass of the system of rods are ...........