How Does Charging a Ball Affect Its Pendulum Motion?

[einsteinette]

HI,

So say you have a small ball hanging vertically below a positively charged plate. When the ball is released from rest with the string at a small angle to the vertical, it swings in periodic pendulum motion. If the ball is now positively charged, does the period increase, decrease or stay the same? And why?

- Well at first, when it's neutral, there would be a slight attraction between the ball and the charged plate. But when the ball becomes positive as well, there would be now a slight repulsion. So would it stay the same?

 

[JaWiB]

Do you know the differential equation for a simple pendulum? You could derive a similar equation with the electric force included. The solution should have the same form, so the period should be fairly obvious