Three uniform Spheres each of mass M and radius R are kept on horizontal surface in such a way that each touches the other two.

Question

Answer 1

Each of the spheres can be assumed to be masses located at the center of the sphere of mass m. Hence the three spheres will constitute three particles each of mass m located at vertices of equilateral triangle of side 2r. Force on each mass due to the other sphere will be 

Note that F1 and F2 will be oriented along two side of the equilateral triangle at an angle of 60⁰ .
Resultant force on each sphere