A uniform ring of mass m is lying at a distance a form the centre of a sphere of mass M just over the sphere (where a is the radius of the ring as well as that of the sphere). Then magnitude of gravitational force between them is
For a small mass dm, distance from the center of sphere is 2a. force along ‘dm’
Component of force F sin get cancelled net force 2Fcos .
For the entire ring-
field intensity due the ring at the centre of the sphere is