Question

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?

Answer 1

The force is `=-7*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(q_1q_2)/r^2`

where k is a constant:

`k=9*10^9NmC^-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=7C`

`q_2=-9C`

`r=9m`

`F=(9*10^9*7*(-9))/9^2`

`=-7*10^9 N`