1. The problem statement, all variables and given/known data A runner has a mass of 168 Kg and is traveling North at 5 meters per second. Another runner is traveling South at 5 meters per second. They collide and come to a complete stop. What is the mass of the second runner 2. Relevant equations I do not have an equation. 3. The attempt at a solution I have stayed up all night trying searching on the Web to find out anything.