A student rubs a balloon against her hair. She then places the side of the balloon against a wall and the balloon sticks to the wall. a) Explain why the balloon sticks to the wall.
b) If the balloon is turned around so the other side touches the wall, will the balloon stick to the wall? Justify your answer.

Suppose that a cylindrical tank 6 meters high with a radius of 2 meters is filled to the rim with water. the tank is buried so that the top of the tank is 1 meter below ground level. the space above the tank is not filled with water. calculate how much work needs to be done by a pump to pump the water out of the tank up to ground level. (the water weighs 9,800 newtons per cubic meter.)