A thin uniform spherical shell has mass $M$, radius $R$ and centre O. A particle of mass $m$ is held inside it, at a distance $R/2$ from O, as shown in the figure. Take the gravitational potential to be zero far away. Which of the following statements are correct?

Fig. 1: A thin spherical shell of mass M and radius R with centre O. A small particle of mass m is inside the shell at a distance R/2 from O.