Physics - Electrostatics Question with Solution | TestHub

Two charged balls are connected by an inextensible thread of length $3m$. Masses of balls are $2kg$ and $1kg$, the charges are $+20\mu C$ and $-100\mu C$. What minimum constant external force $F$ (in $N$ ) must be applied to the ball of mass $1kg$ so that the thread does not slack? Neglect gravity and friction.