Leaf Blower Nonsense

What you need

  • A leaf blower
  • Some toilet rolls
  • The cardboard tube from a roll of cling-film or aluminium foil
  • The end of a cardboard box
  • Some tape

What you do

  1. Cut a disc out of the cardboard box, larger in diameter than your toilet rolls, and cut a hole in the middle of this just large enough to pass the long cardboard tube through. Do that, and tape the disc in place, so you've made what looks a bit like a very short stubby sword with a handguard. We'll call it a 'handle.' You can also use a paint roller for this, just make sure your hand is protected from the toilet roll.
  2. Hold the handle with one hand, and put a toilet roll on the end your hand isn't holding. If you're doing this right, the guard should be between your hand and the toilet roll. Tilt the whole thing so the toilet roll is leaning into the guard, and finally make sure the loose flap of toilet paper is draped over the top of the roll, facing away from you.
  3. Now, aim the leaf blower high, turn it on, and very carefully bring the toilet roll up so it is just beneath the flow of air.

You should find that the airflow spools the toilet paper off the roll, sending it flying high in the air and emptying the roll in seconds. This is quite (a) funny, (b) spectacular and (c) ecologically unsound... so we're not recommending you do it too often. But it's fun while it lasts.

What's going on?

This is an example of the Bernoulli effect, where fast-moving air is at a lower pressure than the slow moving air around it. In this case the air from the leaf blower is at a low pressure. When you bring the toilet paper close to it, the high-pressure air beneath it lifts the paper and shoves it into the air stream. It's accelerated by the air stream, and that sends the arc of paper spooling out across the playground.

Special Safety advice

Make sure the cardboard disc guards your hand from the fast-spinning toilet roll. It's possible to collect a nasty friction burn if you're not careful. A leaf blower is a power tool so make sure you follow its instructions and this should be done outside. It isn't advisable to point the leaf blower at someone.