1. The problem statement, all variables and given/known data If a curve with a radius of 60 meters is properly banked for a car traveling 60 km/hr, what must the coefficient of friction be for a car on the same curve traveling 90 km/hr? 2. Relevant equations Fmax = u * Fn where Fmax = force causing the friction, u = coefficient of friction, and Fn = normal force 3. The attempt at a solution I'm beginning to think I don't really understand uniform circular motion. I read through my book's examples but they're not very helpful. What does a car traveling around a curve 60 km/hr tell us about a car traveling around the curve at 90 km/hr? Is the problem saying that the coefficient of friction was zero in the first case, or that it just increased? I don't understand where to begin with these problems.