Which of Newton's Laws explains the behavior of a rocket motor?

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This principle is fundamental in understanding how rocket motors operate. When a rocket engine expels gas out of its exhaust at high speed, this action generates a force that propels the rocket in the opposite direction.

This law effectively explains the mechanism behind why rockets are able to launch and navigate in space. The expulsion of gas downwards creates an upward thrust that moves the rocket upwards, overcoming gravitational pull. The efficiency of a rocket's design, including how it manages the reaction of expelled gases, directly correlates with the practical application of this law.

The other laws of motion and gravitation, while important in their own contexts, do not specifically describe this action-reaction relationship in the context of rockets. Newton's First Law focuses on inertia, and the Second Law relates force, mass, and acceleration, neither of which directly capture the essence of how rockets function through the propulsion mechanism defined by the Third Law. Newton's Law of Gravitation pertains to the attraction between masses but does not explain the propulsion process in a rocket motor.