With the engines off, a spaceship is coasting at a velocity of +250 m/s through outer space. The ship carries rockets that are mounted in firing tubes, the back ends of which are closed. It fires a rocket straight ahead at an enemy vessel. The mass of the rocket is 1200 kg, and the mass of the spaceship (not including the rocket) is 2.0 106 kg. The firing of the rocket brings the spaceship to a halt. What is the velocity of the rocket? I used the equation vcm=(m1*v1+m2*v2)/(m1+m2) but the answer I got is wrong. Please help ASAP!!