The Law of conservation of momentum states that the linear momentum of the system is always conserved for an isolated system. Rockets also work on this law. The momentum of fuel ejected is transferred as the momentum of the rocket flying.
A rocket works by expelling gases from one end at a very high velocity. The escaping gases have a very high speed, which translates to tremendous momentum. Due to the principle of conservation of momentum, the body of the rocket is pushed forward. If both the momentum of the gases and that of the rocket are added, the sum is zero.
- The linear momentum of one or more objects is conserved when no external forces act on those objects.