Hi, sorry if this is in the wrong forum. I have a physics problem I do not understand: Jim is removing a piece of plastic wrap from a large roll. However, he is finding that this is difficult because the piece of plastic wrap keeps trying to stick to the roll. If the charge on the piece of plastic wrap is +3*10^-7 C, what is the charge on the roll of plastic wrap? How do you know this? I know the plastic wrap roll is negative charge, and that's about it. Help!