1. The problem statement, all variables and given/known data A runner sprints around a circular track of radius 100m at a constant speed of 7m/s. The runner's friend stands 200m from the center of the track. How fast is the distance between the friends changing when the distance between them is 200m? 2. Relevant equations 3. The attempt at a solution I'm having a hard time setting this problem up. I drew a picture but honestly that wasn't of much help to me, I'm stuck :/.