posted by Robbie .
A spaceship of mass 2.0×106kg is cruising at a speed of 4.6×106m/s when the antimatter reactor fails, blowing the ship into three pieces. One section, having a mass of 5.2×105kg , is blown straight backward with a speed of 2.2×106m/s . A second piece, with mass 7.7×105kg , continues forward at 1.3×106m/s .
1)What is the speed of the third piece? Assume that the initial speed of the ship is positive.