Question

Two identical charges, 3.0 m apart, exert forces of magnitude 5.0 N on each other. What is the value of either charge?

Answer 1

Force

$F=\frac{kq_1q_2}{r^2}$

$F=\frac{kq^2}{r^2}$

$q=\sqrt\frac{Fr^2}{k}$

$$q_1=q_2=q=\sqrt\frac{5\times9}{9\times10^9}=70.71\mu C$$