The Wind powered balloon pinwheel is an example of Newton’s Third Law of Motion, which states that for every action there is an equal and opposite reaction. When you have blown up a balloon and let it go you’ve experienced this law by watching the balloon fly around as the air comes out. Air has mass and is made of molecules. The air molecules that are pushed out of the balloon push against the molecules in the atmosphere creating a reaction force called thrust that acts on the balloon. Thrust acts on the balloon with equal force, and in the opposite direction as the air that is squeezed out.
Rockets are launched using the same principle: Rocket boosters are full of combustible fuel. Rocket fuel gases quickly expand and rush out through the exhaust nozzle. This air creates thrust powerful enough to propel the rocket upward out of the earth’s atmosphere. In the case of our rocket pinwheel the balloon forces air out through the straw. Thrust causes the balloon to spin around in a circular motion.