45. A thin silk thread withstands a tension of 9.80 mN. A ball weighing 670 mg suspended on this thread has a charge of 1.1 ∙ 10−8 C. From below, in the direction of the suspension line at a distance of 1.80 cm, a ball having a charge of the opposite sign is brought to it. At what charge can the thread break?

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