80. Two balls of the same radius and mass are suspended on the threads so that their surfaces are in contact. After the balls were charged with a charge of 4 × 10–7 C, they pushed off from each other and separated at an angle of 60 degrees. Find the mass of the ball if the distance from the suspension point to the center of each of the balls is 20 cm.

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