The Greek scientist Archimedes once claimed that if he had a point of support, he'd be able to move the world. He was referring to the lever's amazing ability to make heavy lifting easier. In the following demonstration a child uses a lever to lift an adult.
wood block or brick
plank of wood, 1" thick and at least 4 feet long
Note: If these materials are not available, use a playground seesaw as in IDEAS FOR DISCUSSION #1.
Make a lever by placing the plank over the wood block. To take advantage of the properties of the lever, make sure the fulcrum (wood block) is closer to the end of the lever on which the adult will stand. Have the adult stand on the short end. Have the student stand on the long end. What happens? If the student cannot lift the adult, adjust the fulcrum so that it is closer to the side on which the adult is standing.