I recently ran into something between two teachers. For the longest time one has been teaching that when a car is traveling in circular motion on a banked track with friction, only the horizontal component of the friction force is to be taken into account, by adding to the centripetal force; the friction force of course being parallel to the banked track. However, another teacher has told me that the vertical component is taken into account, and this significantly complicates things. Since the car is not moving up or down along the incline, all vertical forces must cancel out. So the vertical component of the normal force must equal (in magnitude) the force of gravity and the vertical component of friction. But friction depends on the normal force. I've attached a diagram of the situation and the solutions, (using mathtype) as images to make sure you understand what each teacher is suggesting. What I want is a second opinion; do you take the vertical component of friction into account or not? Thanks in advance.