A mass m is placed at point P lies on the axis of a ring of mass M and radius R at a distance R from its centre. The gravitational force on mass M is

For a uniform ring of mass M and radius R at its centre

For a uniform ring of mass M and radius R at its centre

A point P lies on the axis of a fixed ring of mass M and radius R , at a distance 2R from its centre O . A small particle starts from P and reaches O under gravitational attraction only. Its speed at O will be

A point P lies on the axis of a fixed ring of mass M and radius a , at a distance a from its centre C . A small particle starts from P and reaches C under gravitational attraction only. Its speed at C will be.

A point P lies on the axis of a fixed ring of mass M and radius a , at a distance a from its centre C . A small particle starts from P and reaches C under gravitational attraction only. Its speed at C will be.