Three particles, each of mass m, are placed at the vertices of an equilateral triangle. What is the force acting on a particle of mass 2m placed at the centroid D of the triangle ?

Explanation

The positions of the particles are shown in Fig.1.25.

Let DA=DB=DC=x.
The gravitational forces on the particle at D, due to the particles at A,B,C are equal , with value
`(G(2m)(m))/(x^2)` directed as shown in the figure.
By symmetry the resultant force on 2m =0