Three uniform spheres each of identical mass and radius are kept in such a way that each one touch the other two spheres. We need to find the total gravitational force acting on each sphere and the problem is as shown in the diagram below

Solution

On any one sphere, there is gravitational force due to the other two and to find the resultant force, we need to use vector laws of addition. Distance between any two spheres centers is nothing but twice the radius of any sphere.