Question

Two pith balls of mass 0.2 gm each are suspended by two nylon strings of length 50 cm each.They are charged with charge of equal magnitude and same nature. If they come to rest after repulsion at a distance of 4 cm, then find the charge on each ball.

Answer 1

Here, Distance between two charges

If there is Q change on each pith ball, then repulsion force between them

weight of each pith ball = mg

= 0.2 x 10^-3 kg x 9.8 m/s = 0.196 x 10^-3 N

Suppose tension on each string = T since,pith ball is in equilibrium, so the algebric sum of moments of force acting on them will be zero.

ie, F x OC - mg x AC + T  x O = 0