Two small identical metal balls are equally charged and placed at a fixed distance away from each other. They experience the electrostatic force ' F ' A similar uncharged ball after touching one of them is placed at the middle point between the two balls. The force experienced by this ball is

Step-by-step solution

The force between equally charged identical balls is: F = kQ ^2 r ^2 When a similar uncharged ball, touches one of them. This ball aquires a charge Q 2 and the ball being touched looses Q 2 . Now, the force experienced by the third ball is given by, F _ net = F ₁- F ₂ where, F ₁= kQ ^2 / 2 ( r 2 )^2 = 2 kQ ^2 r ^2 is the repulsion from the first ball and F ₂= k ( Q 2 )^2 ( r 2 )^2 = kQ ^2 r ^2 is the repulsion from the second ball. F _ net = F ₁- F ₂= 2 kQ ^2 r ^2 - kQ ^2 r ^2 = F