Loop the Loop

What you need

• Two polystyrene cups
• Two large elastic bands
• Sticky tape

Instructions

1. Tape the two polystyrene cups together at the base
2. Tie the two elastic bands together
3. Hold one end of the elastic where the cups join and wind it around a few times until the other end of the elastic is at the bottom and pointing away from you
4. Hold the cups in one hand and stretch the elastic with the other
5. Fire the cups like a catapult

Results and Explanation

Once you've had a bit of practice, the cups will soon be looping in the air.

This is because elastic makes the cups spin backwards as well as move forward through the air. This back spin creates lift, forcing the cups upwards. But air resistance soon slows the cups down and they fall towards the ground, completing the loop.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.