A car is on a banked curve, following a path which is part of a circle with radius $R$. The curve is banked at angle $\theta$ with the horizontal, and is a frictionless surface. What is the speed the car must go to accomplish this?
What I don't understand about this problem is why we assume there is only the normal force and the gravitational force on the vehicle. From that point onwards, I have no trouble following the solution.
The way I see it, if we're considering only that there exists a normal force and a gravitational force, something the car is doing (accelerating?) must be "adding" to the normal force. Or is it possible that the car could just be coasting, and it could keep a constant height along the banked curve?