Railroad and Highway Curves
Railroad curves are much like highway curves. Infact, when highways were first being built in the United States, they used railroad standards. To understand motion on a curve, we will use a vehicle on a highway since there is little to no difference between that and train.
=> The net force on a car traveling around a curve is the centripetal force, Fc = m v2 / r, directed toward the center of the curve.
=> For a level curve, the centripetal force will be supplied by the friction force between the tires and roadway.
=> A banked curve can supply the centripetal force by the normal force and the weight without relying on friction.