A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig bladder. Some balloons are used for decorative purposes, while others are used for practical purposes such as meteorology, medical treatment, military defense, or transportation. A balloon's properties, including its low density and low cost, have led to a wide range of applications. The inventor of the rubber balloon, (the most common balloon) was Michael Faraday in 1824, via experiments with various gases.
The concept behind the Balloon Powered Car is pretty simple, but that doesn't make it any less impressive! When you blow up the balloon, set your racer down, and let it go, escaping air from the balloon rushes out of the straw causing propulsion. The principle at work is Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. In the case of the Balloon Powered Car, the action is the air rushing from the straw. The reaction is the movement of the car! The moving Balloon Powered Car has kinetic energy, but even an object that isn't moving has energy. This energy is called potential energy. The potential energy of the car is in the elastic material of the balloon. As the balloon fills with air, it builds more potential energy. As the air flows from the balloon, it changes to kinetic energy. This is the conservation of energy. The baloon helicopter works in the same way but doesn't have to contend with friction of the table.