charge and point charge
\( \vec{F}=\frac{1}{4\pi\varepsilon_0}\frac{q_1q_2}{r^2}\hat{r} \)
\( q_1 \) = charge on first particle (C)
\( q_2 \) = charge on second particle (C)
\( r \) = distance between charges (m)
\( \varepsilon_0 \) = permittivity of free space (C^2 N^-1 m^-2)