Final answer:
The force between two charged spheres is due to their charges. If one sphere is uncharged, the repulsive electrostatic force becomes zero.
Step-by-step explanation:
Coulomb's Law and Electric Forces
When two plastic spheres with uniform charge repel each other with a force of 10 N, this repulsion is due to the electric charges on each sphere. According to Coulomb's law, the force between two charged objects is directly proportional to the product of the charges on the two objects and inversely proportional to the square of the distance between them. If the charge is removed from one of the spheres, there will no longer be a repulsive force due to electrical charges. Therefore, the force between the two spheres will be zero because one of the spheres now lacks charge, thus not contributing to an electrostatic force, and the answer will be (d) zero.