75. A small ball weighing 2 ∙ 10−3 kg, suspended on a thin silk thread, carries a charge of 3 ∙ 10−7 C. What is the distance from below to bring another small ball with a charge of 5 − 10−7 C, so that the thread voltage decreases by 2 times?

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