The law of motion that explains rocket propulsion is Newton's Third Law of Motion.

Here's how it works:

* Action and Reaction: Newton's Third Law states that for every action, there is an equal and opposite reaction.

* Rocket Propulsion: A rocket engine burns fuel, which creates hot, expanding gases. These gases are expelled out of the rocket's nozzle at high speed (action). The rocket, in turn, experiences an equal and opposite force pushing it in the opposite direction (reaction). This is what propels the rocket forward.

In simpler terms, the rocket pushes the hot gases out the back, and the gases push the rocket forward.