Question

Two equal charges are located 1m from each other. The force acting between them is 2N. How many Coulombs is each charge?

Answer 1

Given:

$q_1=q_2=q$

$r=1\:\rm m$

$F=2\:\rm N$

The Coulomb's law says

$$F=k\frac{q_1q_2}{r^2}=k\frac{q^2}{r^2}$$

Hence, the charge of each point

$$q=\sqrt{Fr^2/k}=\sqrt{2*1^2/9*10^9}=1.5*10^{-5}\:\rm C$$