# What is the force, in terms of Coulomb's constant, between two electrical charges of 18 C and -15 C that are 9 m  apart?

Jan 29, 2016

If ${q}_{1}$ and ${q}_{2}$ are two charges seperated by a distance $r$ then the electrostatic force $F$ between the charges is given by

$F = \frac{k {q}_{1} {q}_{2}}{r} ^ 2$

Where $k$ is the Coulomb's constant.

Here let ${q}_{1} = 18 C$, ${q}_{2} = - 15 C$ and $r = 9 m$

$\implies F = \frac{k \cdot 18 \left(- 15\right)}{9} ^ 2$

$\implies F = \frac{- 270 k}{81}$

$\implies F = - 3.3333333 k$