Three charges +5 q, Q and -2 q are kept along a straight line in the same order such that, +5 q and -2 q charges are at a distance of 2 r 3 and r 3 from the charge Q respectively. If the net force on the charge -2 q is zero, then Q is

Step-by-step solution

The given situation is shown below. Since, net force on charge (-2 q) is zero, Therefore, charge Q must be positive so that there are two opposing forces on charge -2 q . Now, F_ net =0 i.e. F(5 q,-2 q)=F(Q,-2 q) K .5 q (-2 q) r^2 = -K . Q 2 q ( r 3 )^2 10 q=2 9 Q Q= 5 9 q