Spinning Juice

Finished your drink of juice? Great! No don’t throw away the empty carton! Here’s something fascinating….

Adult supervision required.

You will need:

empty 1 litre fruit juice carton
piece of string
pair of scissors
washing up bowl
water

What to do:

Poke a hole in the bottom left hand corner of each of the four faces of a 1 litre juice carton. (children should be helped with this bit by adults)
Poke an extra hole in the top flap of the carton and tie a string through it.
Hang the carton from the string.
Pour some water into the washing up bowl so that it is about one quarter full.
Place the carton into the bowl of water.
Pour water into the carton until it is full to the top.
Now lift the carton out of the water by the string and watch what happens!

What’s going on?

Newton's Third Law states that every action has an equal and opposite reaction. Water shoots out the holes, and pushes back on the carton with equal force. A turbine is formed as the energy of the moving liquid is converted into rotational energy. Consequently the carton spins. This effect was first noted by Hero of Alexandria.

Hero (or Heron) of Alexandria (roughly A.D. 10 to roughly A.D. 70) was a Greek engineer and geometer. His most famous invention was the first documented steam engine, the aeolipile. Steam was generated in a separate boiler and fed into a sphere through a hollow spindle. The steam left the sphere via two narrow, angled nozzles and the reaction to the jets of steam leaving these nozzles made the sphere spin.

To see an animation of Hero’s Aeolipile click here.