# What is the force, in terms of Coulomb's constant, between two electrical charges of 8 C and -2 C that are 9 m  apart?

This question simply requires Coulomb's Law: $F = \frac{k {q}_{1} {q}_{2}}{r} ^ 2$. The answer is requested in terms of Coulomb's constant, and is $F = \frac{k \cdot 8 \cdot - 2}{9} ^ 2 N = \frac{- 16 k}{81} N$.
Coulomb's constant, the $k$ in the equation, is $9 \cdot {10}^{9} N {m}^{2} {C}^{-} 2$, but in this case we have been asked to answer in terms of this constant, so we express the answer in terms of $k$.