# What is the force, in terms of Coulomb's constant, between two electrical charges of -105 C and 90 C that are 15 m  apart?

Sep 21, 2017

$F = - 42 k$

#### Explanation:

${q}_{1} = - 105 C$
${q}_{2} = 90 C$
$r = 15 m$

$F = \frac{k {q}_{1} {q}_{2}}{r} ^ 2 = \frac{k \left(- 105\right) \left(90\right)}{15} ^ 2$
$= \frac{- k \left(105\right) \left(6\right)}{15} = \left(- k \left(21\right) \left(2\right)\right) = - 42 k$

$k = \text{Coulomb's Constant} = 9 \cdot {10}^{9} \frac{N - {m}^{2}}{C} ^ 2$