A railroad car containing explosive material is initially traveling south at a speed of 4.9 m/s on level ground. The total mass of the car plus explosives is 2.9 104 kg. An accidental spark ignites the explosive, and the car breaks into two pieces, which then roll away along the same track. If one piece has a mass of 1.9 x 104 kg and a final speed of 2.0 m/s toward the south, what is the final speed of the other piece?