We were doing an experiment today and we had 2 aluminum foil balls hang next (but not touching) to each other. Both were initially grounded then we charged one of them while the other remained neutral. We observed an attraction between them but coulomb's law states that: F = k(q1*q2/r^2). If one ball was neutral (zero charge) then it should result with no attraction nor repulsion. I realize that this experiment may have other influencing factors such as humidity but theoretically this assumption should be true right?