The problem reads: A banked circular highway curve is designed for traffic moving at 60 km/h. The radius of the curve is 200 m. Traffic is moving along the highway at 40 km/h on a rainy day. What is the minimum coefficient of friction between tires and road that will allow cars to take the turn without sliding off the road? (Assume the cars do not have negative lift.) I managed to solve for the angle of the bank through the equation angle = tan^-1((v^2)/gR). Where v=velocity, g=the acceleration of gravity, and R=the radius of the curve. My trouble is that after I solve for the angle I cannot think of anyway to solve for static friction without the weight or mass of the car. Am I thinking in the wrong direction to believe that i need the mass of the car? It would be very appreciated if someone could point me in the right direction on this problem. Thanks.