Задача 31291.

Horizontally arranged disk radius R, uniformly charged with a surface density of sigma. Small ball with a charge q is above the center of the disk in a state of equilibrium at a height h = R. Find the mass of the ball.

Detailed solution shorthand terms, formulas, laws used in the decision, the withdrawal of the calculation formula and the response.
If you have any questions to address, please. I´ll try to help.