A metal spherical surface is grounded. Inside and outside the sphere is vacuum. Within the sphere there is a negative point charge q at a distance a from the center M.
a) What are the magnitude and direction of the force F on q?
b) Determine the lowest and highest values of the density of the surface charge s.
c) Say the spherical surface was not grounded, but has a potential V. How large are the charges on the inside and outside of the sphere?