When rocket has burnt its fuel what happens?

Answer 1

There are usually about 3 compartments in a rocket and when one compartments fuel has run out, it breaks off and burns up into the atmosphere or lands in the ocean somewhere where no one is. Then the rocket begins to use up the next compartment.

Answer 2

Once the rocket has burnt all of its fuel, it will no longer have the thrust needed to continue accelerating. The rocket will eventually reach its maximum velocity and will continue on its trajectory until other forces, such as gravity, cause it to slow down and eventually fall back to Earth or continue on its path through space.