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

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

(a) $\frac{G M m}{R^2}$

(b) $-\frac{G M m}{R^2}$

(c) Zero

(d) $ 4 \frac{G M m}{R^2}$

Ans: (c)