Conservation of momentum. Jet motion

Jet (reactive) motion is the motion that results when part of a body separates from it at some velocity and the rest moves in the opposite direction. A rocket expels burning fuel gases backward at high speed and, by conservation of momentum, moves forward: m_gas υ_gas = M_rocket υ_rocket (in magnitude, starting from rest). Jet motion works even in empty space, because the rocket does not push on air but on the gas it expels. It also occurs in nature: squid and octopuses squirt water and swim the other way. Rockets are used to launch satellites and in spacecraft and aircraft. K. Tsiolkovsky, one of the founders of astronautics, developed the theory of rocket motion.