1. The problem statement, all variables and given/known data The left end of a spring is attached to a wall. When Bob pulls on the right end with a 200N force, he stretches the spring by 20cm. The same spring is then used for a tug-of-war between Bob and Carlos. Each pulls on his end of the spring with a 200N force. How far does Carlos's end of the spring move? 2. Relevant equations Hooke's Law, Newton's Second Law 3. The attempt at a solution Using the fact that the spring pushes back with a -200N force, I found the spring constant to be: F(spring) = k * s => -200N = -k * 0.2m => k = 1000N/m However, I have no idea what to do with this information. When Carlos and Bob have their tug-of-war, the net force should be 0 on the spring, which leads me to believe Carlos's end of the spring is going nowhere (0cm). I tried this answer, however it turns out that it is wrong. I know this problem cannot be as hard as I am making it...so any help would be greatly appreciated.