An inflated balloon contains air under pressure. That air flows out when the neck of the balloon is opened, which creates a driving force. You can use this to sail a little boat, for example.
Ask a grown-up to help you with this step. Use the little boat shown in the photograph as an example. Cut out a piece of wood shaped like a boat (use a saw that is suitable for the type of wood you are using for your boat). Sandpaper the edges.
Attach the piece of garden hose to the boat, using the bracket. Make sure it is long enough that a balloon can be attached to the top and that the bottom end is in the water.
Inflate the balloon. Seal the neck using a clothes peg, so the air can’t escape. Attach the balloon to the piece of garden hose on the boat.
Remove the clothes peg! Is the boat sailing now?
What did you discover
When you open the neck of the balloon, the air inside escapes. As it leaves the balloon, this air first comes into contact with the water. The air pushes the water away, which gives the boat a push in the opposite direction, and the boat sails off.