Question

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?

Answer 1

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=(kq_1q_2)/r^2`

Where `k` is the Coulomb's constant.

Here let `q_1=18C`, `q_2=-15C` and `r=9m`

`implies F=(k*18(-15))/9^2`

`implies F=(-270k)/81`

`implies F=-3.3333333k`

Note: Negative sign indicates that the force is attractive.