Physics static electricity help!!! 10 points for good help!!!!?

[J.A.]

Any help would be nice on this question.If you cannot help please don't reply!!!


Benjamin Franklin once wrote that he had "erected an iron rod to draw the lightning down into my house, in order to make some experiment on it, with two bells to give notice when the rod should be electrify'd..." The chime had two small bells mounted side by side. One bell was connected to the iron rod for a charge; the other bell was attached to Earth. Between the two bells, a small metal ball was suspended on a silk thread so it could swing back and forth, striking the two bells. Explain why, when one bell was charged, the ball would keep swinging, hitting first one bell then the other.