Final answer:
The interactions in each scenario described revolve around Coulomb's law, with forces between charged objects and their movements being determined by electrical repulsion or attraction, as well as gravitational forces.
Step-by-step explanation:
The question involves applying Coulomb's law to understand the interaction between charged spheres. Specifically, it seeks to calculate the forces involved when charges are placed at various distances and configurations, considering both electrostatic and gravitational forces.
When two charged spheres touch, the charges redistribute evenly because spheres of the same size and material have the same charge capacity. The final charge on each sphere is the average of their initial charges. For spheres with charges of -5 nC and -3 nC, the final charge on each sphere after they touch and separate would be (-5 nC + -3 nC)/2 = -4 nC per sphere.
When calculating forces between charged spheres or particles, Coulomb's law dictates that the electrostatic force between two point charges in a vacuum is proportional to the product of the charges and inversely proportional to the square of the distance between them.