Two plastic spheres carry equal charge and repel each other with a force of 10 N. All the charge is then removed from one of the spheres, leaving it neutral, and the spheres are held at the same separation. What is the new force between the spheres?

1. Coulomb's law makes the force proportional to the product of the two charges, q1 times q2. 2. If one charge becomes zero, the product q1 q2 becomes zero no matter what the other charge or the distance is. 3. A zero product gives zero force, so the spheres no longer attract or repel. 4. Assuming the force merely shrinks by half, as in option D, ignores that force needs both charges to be nonzero at once. _Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section 18.2 Coulomb's law_