At what distance from each other are two charges of 10 Coulomb, each interacting with a force of 9mN.

Coulomb’s law states that the force of interaction of two charges F = 1/4 πέέ0 * q1 * q2 / r ^ 2
where q1 and q1 are the magnitude of the charges r is the distance between them, then:
r ^ 2 = 1/4 πέέ0 * q1 * q2 / F
r = √1 / 4 πέέ0 * q1 * q2 / F = √10 ^ -10 * 10 * 10 ^ -9 * 10 * 10 ^ -9 / 9 * 10 ^ -3 = 3 * 10 ^ -12 = 3000 nm …