Put one end on your palm, so the strip extends perpendicularly. Push it down to compress it along its length, then cage it in with your fingers. Open your hand, and it will leap into the air. You can also do this on a table.

When you compress the strip, you are storing potential energy. When you release the strip, the potential energy converts to kinetic energy.

• Availabe pre-made

We usually staple the ends shut, otherwise students think they are finger traps and end up sticking their fingers in the ends, which ruins them.