Answer:
0.702 m
Explanation:
The magnitude of the electrostatic force between two charged objects is given by Coulomb's Law:

where
k is the Coulomb's constant
q1, q2 are the two charges
r is the separation between the objects
And the force is:
- Attractive if the two charges have opposite signs (+-)
- Repulsive if the two charges have same sign (++ or --)
In this problem we have:
is the force between the two balls
is the charge on each ball
Solving for r, we find the separation between the balls:
