5. A charged ball of mass m = 0.4 g is suspended on air from a silk thread in the air. From below, an unlike and equal in value charge q is brought to it at a distance of r = 2.0 cm; as a result of this, the tension force of the thread T increases n = 2.0 times. Find the charge q.

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)