2. Potential frorn charge distribution A washerthat is, a disk with a hole in ithas inner radius a: and outer radius b. The washer has a total charge Q > [I spread uniformly on its surface. It is located in the 333,: plane centered on the origin. (a) Find the potential at any point on the z axis, assuming V = U at innity. Show that your expression is approximated by the potential due to a point charge when E3] \"2) b. (1)) Suppose a proton (charge +6:= mass m) is placed on the z axis at (U: [L a) and then released. How fast will the proton be moving when it is very far from the washer? (Assume it's not so fast as to require relativistic equations.)