You will need: an old CD or DVD (check before you steal your mum’s favourite Take That album!), a sports-bottle cap (Fruit Shoot or similar), a balloon, Blu-tack.
Roll the Blu-tack into a sausage and use it to attach the cap the centre of the CD. Make sure the cap is closed. Inflate the balloon but don’t knot it, then carefully stretch the opening over the bottle cap (it helps if you twist the end of the balloon to stop it deflating while you’re doing this). Your hovercraft is now ready to go! Carefully open the cap and the air will start to escape from the balloon. This makes a ‘cushion’ of air under the CD so you should be able to skim it along a smooth surface (the floor is best). Why not decorate your hovercraft and race it against your friends?
Think like a scientist:
- Try skimming it without the balloon (or with the cap closed), what do you notice?
- The cushion of air reduces friction between the CD and the floor, can you find out more about friction?
- Does the size of the balloon make a difference?