College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 65

A tiny sphere of mass 8.00 g and charge 2.80 nC is initially at a distance of 1.60 mm from a fixed charge of +8.50 nC. If the 8.00- g sphere is released from rest, find (a) its kinetic energy when it is 0.500 m from the fixed charge and (b) its speed when it is 0.500 m from the fixed charge.