You decide to do a demonstration on a rooftop that requires water. There isn't a handy faucet, so you put a barrel of water down in the plaza. The top of the barrel is open to the atmosphere. One end of a long plastic tube (2 cm diameter) goes into the barrel and the other end goes into a vacuum pump up on rooftop. You begin sucking water up through the tube. Eventually, you have a tube where the water is static. What is the absolute pressure in the tube at the rooftop? Are there any problems with making this work? Draw a sketch and use calculations to support your explanation.