Newtons second law describes the affect of net force and mass upon the acceleration of an object. P2 dmvu where u is the exhaust gas velocity with respect to the rocket. The exact relationship is Fma where m is the bodys mass.
In a small time dt the momentum of the rocket becomes.
F k ma. The second law states that the acceleration of a body is equal to the force acting upon it divided by the bodys mass. Because the standard unit of mass is the kilogram kg and the standard unit of acceleration is meters per second squared ms2 the unit for force must be a product of the two -- kg ms2. For a body with a constant mass m force is given by F ma.