A metal sphere has radius R and mass m. A spherical
hollow of diameter R is made in this sphere such that its
surface passes through the centre of the metal sphere
and touches the outside surface of the metal sphere.
A unit mass is placed at a distance from the centre of the metal
sphere. The gravitational field at that point is
(a) ((GM)/R^2 ) (1−(1/(8(1−((2R)/a))^2 )))
(b) ((GM)/a^2 ) (1−(1/(8(1−(R/(2a)))^2 )))
(c) ((GM)/((R+a)^2 )) (1−(1/(8(1−(R/(2a)))^2 )))
(d) ((GM)/((R−a)^2 )) (1−(1/(8(1−((2a)/R))^2 )))