On which one of the following conservative laws, does a rocket work ?

A rocket operates based on the law of conservation of linear momentum, which is a direct consequence of Newton's Third Law of Motion [t2][t7]. According to this principle, the total momentum of a closed system remains constant if no external forces act upon it [t1]. In rocket propulsion, the engine ejects high-velocity exhaust gases in one direction (downwards). To conserve the total linear momentum of the system, the rocket must experience an equal and opposite momentum in the other direction (upwards), resulting in thrust [t3][t6]. This relationship is defined by the product of mass and velocity [t1]. While Newton's Second Law explains the magnitude of acceleration based on thrust and mass, the fundamental governing conservative law for the propulsion mechanism itself is the conservation of linear momentum [t5][t7].

Sources

1. [1] https://www.grc.nasa.gov/www/k-12/airplane/conmo.html
2. [2] https://www.grc.nasa.gov/www/k-12/rocket/TRCRocket/rocket_principles.html