What's a water rocket?

Rockets are vehicles that move in one direction by launching part of their mass, called reaction mass, in the opposite direction to which they want to go. This happens due to Newton's third law of action-reaction. A water rocket is just a type of rocket that use water as its reaction mass, but to launch it at a high speed it uses compressed air.

The principal parts of most water rockets are:

• Pressure chamber (usually a bottle)
• Guiding system (usually fins)
• Recovery system (usually parachutes)
• Nosecone
• Launcher