A shell of mass M and radius R has another point mass m placed at a distance r from its centre `(r gt R)`. The force of attraction between the shell and point mass is :

A shell of mass M and radius R has point mass m placed at a distance r from its centre. The gravitational potential energy U(r) vs r will be

A point mass m is placed inside a spherical shell of radius R and mass M at a distance R/2 form the centre of the shell. The gravitational force exerted by the shell on the point mass is

A point mass m is placed inside a spherical shell of radius R and mass M at a distance R/2 form the centre of the shell. The gravitational force exerted by the shell on the point mass is

A solid sphere of mass M and radius R has a spherical cavity of radius R/2 such that the centre of cavity is at a distance R/2 from the centre of the sphere. A point mass m is placed inside the cavity at a distance R/4 from the centre of sphere. The gravitational force on mass m is

A solid sphere of mass M and radius R has a spherical cavity of radius R/2 such that the centre of cavity is at a distance R/2 from the centre of the sphere. A point mass m is placed inside the cavity at a distanace R/4 from the centre of sphere. The gravitational force on mass m is

A solid sphere of mass M and radius R has a spherical cavity of radius R/2 such that the centre of cavity is at a distance R/2 from the centre of the sphere. A point mass m is placed inside the cavity at a distanace R/4 from the centre of sphere. The gravitational force on mass m is

A point mass m_(0) is placed at distance R//3 from the centre of spherical shell of mass m and radius R. the gravitational force on the point mass m_(0) is