rockets

i think Newton's first law can give the reason here see if a spaceship's leaves the earth's atmosphere with a speed v..since there is no external forces acting on it in vaccum so it will continue to move with the same unless it comes in the strong gravitational field of some massive object...

i think it's 3rd law.
the rocket pushes its fuel gases downward due to which it is subjected to a reaction upwards and it goes up.