Find the potential energy of a system of 3 particles kept at the vertices of an equilateral triangle of side r.

Find the potential energy of a system of four particles each of mass 2m kept at the vertices of a square of side x. Also find the potential at the centr of the square.

Find the potential energy of a system of four particles each of mass 2m kept at the vertices of a square of side x. Also find the potential at the centr of the square.