About 35 electron volts of energy is required to ionize an air molecule. A 2 MeV radioactive particle passing through the air would therefore be expected to result in the ionizing of approximately ___ air molecules.

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.)