What is action and what is reaction in a rocket motor?
The action is the downward movement of the hot gases, while the reaction is the upward movement of the rocket, which is propelled by this physics principle. The hot gases are generated inside the combustion chamber when the fuel burns; thus, the gases are a form of energy. When the rocket was first used, it was a new form of driving force. The action and reaction principle is what makes a rocket motor different from an internal combustion engine, whose driving force is the rotatory movement of the axle imparted by the moving pistons.