Question

A uniform spherical shell gradually shrinks maintaining its shape. The gravitational potential at the centre
(a) increases
(b) decreases
(c) remains constant
(d) oscillates.

Answer 1

(b) decreases
AS it is maintaining its shape so its mass will remain constant which implies that if it shrinks then its volume decreases and to keep the mass constant ,its density increases.Also the gravitational potential at the centre of a uniform spherical shell is inversely proportional to the radius of the shell with a negative sign. When a uniform spherical shell gradually shrinks, the gravitational potential at the centre decreases (because of the negative sign in the formula of potential).