Emma52658 Emma52658 03-08-2016 Physics contestada a railroad car with a mass of 30,000 kg is moving at 2.0 m/s when it runs into an at-rest freight car with an equal mass. the cara lock together. what is their final velocity? A. 2.0 m/s B. 0.5 m/s C. 60,000 kg-m/s D. 1.0 m/s