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Milk Carton Generator

Use water to get things really moo-ving

Australian Curriculum links

  • Science > Physical Sciences > Year 4 > ACSSU076
  • Science > Earth and Space Sciences > Year 7 > ACSSU116
  • Science > Physical Sciences > Year 10 > ACSSU229

You’ll need

  • Empty cardboard milk carton
  • Water
  • String
  • Nail
  • Masking tape
  • Scissors
  • Tray to catch falling water

Try this

  1. Using the nail, punch holes in the bottom right hand corner of each side of the milk carton.
  2. Punch a hole in the middle of the top of the carton and tie a piece of string through this hole to hang the carton.
  3. Use masking tape to cover the holes in the bottom, and hang the carton outdoors or over a tray to catch the water.
  4. Fill the milk carton with water.
  5. Take the masking tape off one hole and observe what happens.
  6. Take the tape off the hole opposite to this. Does this make any difference?
  7. Uncover all 4 holes. What happens?

Further investigation

  • Using a new milk carton, try punching the holes in different places on the carton. What difference does this make to the movement of the milk carton?
  • Try changing the size of the holes in the milk carton. Does this affect the movement?
  • Can you make your spinning milk carton do work? Using a pulley and string, you could try and make it winch up an object, or pull an object along the ground.

What’s happening?

Isaac Newton’s 3rd law of motion states that every action has an equal and opposite reaction. The action in this experiment is the water pouring out of the holes. The reaction to this is the force of the water pushing the carton in the opposite direction. The more holes, the faster the carton turns. This is similar to many turbines. Water or steam is forced through holes and is used to make the turbine turn. A shaft connects the turbine to an electrical generator, which makes electrical energy when it is turned.