A3.1 kilogram gun initially at rest is free to move. when a 0.015-kilogram bullet leaves the gun with a speed of 500. meters per second, what is the speed of the gun?

A15,000 kg rocket traveling at +230 m/s turns on its engines. over a 6.0 s period it burns 1,000 kg of fuel. an observer on the ground measures the velocity of the expelled gases to be −1,200 m/s.