Two pith balls each of mass 1g and carrying a charge 1μC are attached to the ends of silk threads 1m long, the other ends of which are attached to some fixed point, in a gravity free space. The force between them is :
As they are in a gravity free space so the force between them is only the electrostatic force. i.e,
F=q24πϵ0r2=9×109(10−6)212=9×10−3N