How To Make A Coin Spin Inside A Balloon

Step 1: You will need

Step 2: Aim

The aim of this experiment is to demonstrate the principle of centripetal force.

Step 3: Method

Place a small coin, like a 5p piece, inside a deflated balloon. Blow up the balloon and tie a knot in it.
Hold the neck of the balloon, where the knot is, in your palm and grip the sides with the fingers of the same hand.
Turn the balloon upside down and twirl the balloon to set the coin in motion.
The coin may bounce around inside the balloon at first but then it will begin to spin. Is it magic? No! It's science!

Step 4: Conclusion

So why did this happen? The coin spun around due to a particular force called 'centripetal force' acting upon it. This is a force that pulls an object towards a central point causing it to move in a circular path around that point. Subjected to centripetal force, the coin was constantly seeking its own centre, and so continued to spin.