You want to prove the law of conservation of energy to a friend. for your demonstration you show that you can use a block and pulley machine to lift 100n with only 20n of input force. what would you say to your friend to explain how is this possible?

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.)