Q 100 We are familiar with dropping a rock (a mass) from rest and watching it fall( in a gravitational field). (If there were no friction, we could have just as much fun filling a helium balloon, and "dropping" the balloon.) a) Describe the motion of the rock, and the changes in kinetic and gravitational potential energy it experiences. b) Release a positive charge from rest in the center of an area with a uniform electric field. Describe the motion of the charge, and the changes in kinetic and electric potential energies that it experiences. Now describe the difference in potential it experiences. c) Release a negative charge from rest in this same place in electric field. Describe the motion of the charge, how is what happens to it different? d) Describe the circumstances and motion of a helium balloon as an analogy for c)