The charges of two identical aluminum speheres are -24uC and +4.0uC. The spheres are brought together so they simultaneously touch each other. They then separated and placed on the X-axis. What is the net force exerted b one sphere on another after seperation?

Answer 1

add the charges, then divide the result by 2, that is the net charge on each.

Now, to compute the force, you need the radius of the spheres to get the separation.