To make a Hovercraft, poke a hole in the center of a plastic
plate with a ballpoint pen. Poke another hole in the center of the bottom of a
film canister. Put the film canister over the hole in the plate and use poster
putty to stick it on. Blow up a balloon and twist the opening so that air
doesn't come out. Stretch the opening of the balloon over the film canister.
Make sure that the opening of the balloon lines up with the hole in the film
canister. Put the Hovercraft on a smooth, flat surface, let go of the balloon
and give it a flick. The Hovercraft will glide across the surface on a cushion
of air. The air in the balloon has to go somewhere. So, it flows out of the
balloon and goes under the plate. The layer of air under the plate takes up
space so it keeps the plate and table from rubbing on each other. When objects
rub against each other, they create friction. Friction drags on each object and
slows it down. The Hovercraft has very little friction because it rests on air.
idea courtesy of
ZOOM at PBS Kids