Question

Two negative charges that are both -3.0 C push each other apart with a force of 19.2 N. How far apart are the two charges ?

Answer 1

The Coulomb's force acting between two charges is

`F=k_e (q_1 q_2)/(r^2)`
where
`k_e = 8.99 \cdot 10^9 N m^(-2)C^(-2)` is the Coulomb's constant, q1 and q2 the two charges, and r the distance between them.

Using
`q_1 = q_2 = -3 C`, we can find the distance between the two charges when the force is F=19.2 N:

`r= \sqrt{k_e (q_1 q_2)/(F) }= \sqrt{ 8.99\cdot 10^9 ((-3.0C)^2)/(19.2 N) }=6.5 \cdot 10^4 m = 65 km`