Remember the question from the heat chapter of "which had more heat, the iceberg or the cup of coffee" and while the coffee had the higher average heat, the iceberg was that much bigger therefore had more heat. Consider the above "which one is stronger question". rubbing the balloon on his head was enough for the balloon to stick to his hair, and not fall towards the earth. Let's say he is holding his hair out, so that all the electrostatic force is up, and we only rubbed it enough for the force up to be equal and opposite to gravity. Consider that the force pulling down the balloon is the gravity force stemming from the mass of the entire planet, whereas the force keeping it up is the electrostatic force from ... what?