Gravity Boats

What's this Science Bite about?

Make your own boat and see if you can sail it across your bath or an outdoor pool! Learn about the forces acting upon it including gravity.

Remember - If you are trying these experiments at home you will need the supervision of an adult.

What you will need per boat

The equipment needed to make a gravity boat

  • 2 paper or polystyrene plates
  • A paper or polystyrene cup
  • A straw
  • A pencil
  • Scissors
  • Glue
  • Stickers and pens for decoration
  • A bath or small pool

How to do this experiment

Follow the instructions in the video below.

Can't see the video above? Watch it on Youtube.

  1. Take two paper plates and glue them together, set aside to let them dry.
    Two paper plates being glued together

  2. Use a pencil to make a small hole in the side of the disposable cup 2 cm from its base.
    A pencil, cup and straw
    The hole should be just large enough to push the straw through.

  3. Apply a liberal amount of glue to the bottom of the cup and then stick it down to the centre of the top plate.
    A paper cup with a straw through the side has been attached to a paper plate.
    Make sure the exposed end of the straw is longer than the edge of the plate.

  4. Your boat is nearly finished, it just needs some decorations. Colour it in or apply stickers to the outside of the cup. Don't forget to give your ship a name.
    A Gravity Boat floating on water
    Now place your boat in a small bath or pool and fill its cup carefully until half full with water. Watch as your boat happily sails off, propelled by the water from the straw.

    For even more fun have a race with your friends!

    Two gravity boats in a race

Find out more.

Forces that enable us to move are basically pushes and pulls. When we fill the cup on our boat with water, gravity pulls the water down and it escapes through the straw into the tub or pool. As the water moves out of the straw, it pushes the boat forward. This is an example of Newton’s third law of motion, ever action has an equal and opposite reaction.

Curriculum Links


SCN 1-07a/ 2-07a


Glasgow Science Centre