Question

two point charges Q₁=4.5$uC$ and Q₂=8.5$uC$ are initially very far apart. they are then brought together, with a final separation of 3.5$mm$ . how much work does it take to bring them together?

Answer 1

$$W=k\frac{q_1q_2}{r}\\W=(9\cdot10^{9})\frac{(4.5\cdot10^{-6})(8.5\cdot10^{-6})}{0.0035}=98\ J$$