# What is the force, in terms of Coulomb's constant, between two electrical charges of 7 C and -9 C that are 9 m  apart?

Mar 17, 2017

The force is $= - 7 \cdot {10}^{9} N$

#### Explanation:

Two charged objects, of charge ${q}_{1}$and ${q}_{2}$ separated by a
distance r, exert a force on one another.

The magnitude of this force is given by, Coulomb's Law :

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

where k is a constant:

$k = 9 \cdot {10}^{9} N m {C}^{-} 2$

The direction of the force is toward the second object if the
objects have opposite signs, and away from the second
object if the signs are the same.

Here,

${q}_{1} = 7 C$

${q}_{2} = - 9 C$

$r = 9 m$

$F = \frac{9 \cdot {10}^{9} \cdot 7 \cdot \left(- 9\right)}{9} ^ 2$

$= - 7 \cdot {10}^{9} N$