Electrostatistics (Physics)

Question

Two point charges of -2.0 C are fixed at opposite ends of a meter stick. Where on the meter stick (if anywhere) could (a) a free electron and (b) a free proton are placed so that they are in electrostatic equilibrium (and won't move).

Answer 1

The forces will be cancel for both particles if they are placed at the center of the meterstick. Both situations are unstable. The attraction situation will result in the proton colliding with one of the point charges and the repulsion situation will result in the electron moving perpendicular to the meterstick and accelerating away.