We are learning about hovercrafts. It is easy to make a hovercraft out of an old CD, some bluetack, the lid of a drinks bottle and a balloon.
When we rub our hands together we notice that they become very warm. Rubbing causes friction. We noticed that the CD will not slide too well on the table or floor (because of friction), unless you blow up a balloon and have the air from the balloon go through the drinks lids and under the CD. The CD then floats on a very thin layer of air (too thin to see), and there is no friction (rubbing) between the CD and the floor to slow the CD down when it is gliding on the floor. The game air hockey works in the same way, only the air is pushed up through the table, rather than from the puck! We tried various combinations of CDs and lids, and even a mini hovercraft.