* Fuel Consumption: Rockets burn fuel to generate thrust. As the fuel is burned, it is expelled out the back of the rocket, reducing the rocket's total mass.
* Stage Separation: Most rockets have multiple stages. Each stage is designed to burn its fuel and then separate from the rocket, leaving behind the empty stage and reducing the overall mass.
Important Note: While the rocket's mass decreases, the *total mass* of the rocket and its ejected fuel remains constant. This is due to the law of conservation of mass.
