I have not been able to figure out anything about this problem. I hope somebody will help me. A body of mass 2.0 kg makes an elastic collision with another body at rest and continues to move in the original direction but with one-fourth of its original speed. (A): What is the mass of the other body? (B): What is the speed of the two-body mass center of mass if the initial speed of the 2.0 kg body was 4.0 m/s?