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

The behavior of a rocket motor is best described by Newton's Third Law, which states that for every action, there is an equal and opposite reaction. In the context of a rocket motor, when the propellant is ignited and expelled at high velocity out of the rocket's nozzle, the action of expelling mass generates thrust in the opposite direction. This thrust propels the rocket upward.

This principle is fundamental to the function of rocket propulsion systems. The motor pushes exhaust gases downwards, and in response, the rocket is propelled upwards due to the force generated by this reaction. Understanding this law is crucial for rocketry, as it highlights the mechanics behind thrust generation and the overall flight of the rocket.

Other options, such as the First and Second Laws, describe different aspects of motion and force but do not specifically address the action-reaction pairs that underpin rocket propulsion. The Law of Universal Gravitation pertains to the gravitational forces between two masses and does not relate directly to the functioning of the rocket motor. Therefore, Newton's Third Law is the key concept that accurately describes the operational principle of a rocket motor.