1. The problem statement, all variables and given/known data A van is moving on a horizontal circular bend in the road of radius 75m. The bend is banked at arctan(1/3) to the horizontal. The maximum speed at which the van can be driven around the bend without slipping is 25m/s. Calculate the coefficient of friction between the road surface and the tyres of the van. 2. Relevant equations centripetal force = mv2/r Friction ≤ μR 3. The attempt at a solution See attached diagram. At the maximum speed F=μR. Resolving perpendicular to the plane gives: R = mgcosθ ∴ F = μmgcosθ Resolving in a direction perpendicular to the weight gives: Rsinθ + Fcosθ = mv2/r mgsinθcosθ + μmgcos2θ = mv2/r Solving for μ gives: μ = [(v2/r)-gsinθcosθ]/[gcos2θ] And substituting the values gives μ=0.61. This is apparantly incorrect (the answer should be μ=0.40). I cannot see what I have done wrong. Any hints would be greatly appreciated!