Two pith balls carrying equal charges are suspended from a common point by strings of equal length , the equilibrium separation between them is r. now the strings are rigidly clamped at half the height. The euilibrium seperation between the balls now become

1. r/cuberootof2

2. 2r/under root 3

3. 2r/3

4.(1/under root of 2)raise to power 2