Water rocket
Overview
 
A water rocket is a type of model rocket
Model rocket
A model rocket is a small rocket that is commonly advertised as being able to be launched by anybody, to, in general, low altitudes and recovered by a variety of means....

 using water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 as its reaction mass. The pressure vessel—the engine of the rocket—is usually a used plastic soft drink
Soft drink
A soft drink is a non-alcoholic beverage that typically contains water , a sweetener, and a flavoring agent...

 bottle. The water is forced out by a pressurized gas, typically compressed air
Compressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....

. It is an example of Newton's third law of motion.

The term "aquajet" has been used in parts of Europe in place of the more common "water rocket" and in some places they are also referred to as "bottle rockets" (which can be confusing as this term refers to a firework
Bottle rocket
A bottle rocket is a very small skyrocket. A typical bottle rocket consists of a rocket engine attached to a stabilizing stick. The user can place the stick in an empty bottle , and ignite the rocket engine; the mouth of the bottle guides the stick, stabilizing the rocket in its first moments of...

 in other places).
The bottle is partly filled with water and sealed.
 
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