A uniformly charged thin ring has radius 15.0 cm and total charge 20.0 nC . An electron is placed on the ring's axis a distance 30.0 cm from the center of the ring and is constrained to stay on the axis of the ring. The electron is then released from rest.

Required:
a. Describe the subsequent motion of the electron.
b. Find the speed of the electron when it reaches the center of the ring.