(Coulomb's Law) can anyone tell me if there is any cases in which the electrostatic force between 2 objects is 0?
Eletrostatic force between only two charges never is null. But if there are interactions with 3 or more charges is possible between two of them be null.
Well, just look at Coulomb's law, set it equal to zero, and then see what it would take to make the equation true. Electrostatic force = (a constant number) x (charge#1) x (charge#2) / (distance between them)² = 0 There you have an equation, with some stuff on the left side that's all equal to zero. The stuff is all in the form of one fraction. In order for the fraction to be zero, either the numerator is zero, or else the denominator is infinite. So ? The force is zero if ... -- at least one of the charges is zero, OR -- the charges are an infinite distance apart. If you can arrange for either of those conditions, then you'll have zero force.