Fc is the net inward component of real forces, not an extra force.
This interactive 3D physics simulation demonstrates circular motion on a banked track. Students can explore how the normal force, friction, weight, and inward net force determine the maximum speed of a car moving around a curve.
In circular motion, the centripetal force is the net inward force. It is not an additional force placed on the force diagram. For a car on a banked track, the real forces are weight, normal force, and friction.
For the maximum-speed case, the car tends to slide up the bank, so friction acts down the slope. The inward force is the sum of the inward components of the normal force and friction.
Using vertical equilibrium and f = μN:
The normal force is perpendicular to the banked road surface and has both vertical and inward components.
At maximum speed, friction acts down the slope and contributes an inward component.
The inward components of real forces provide the centripetal acceleration.
The maximum speed depends on the curve radius, bank angle, gravitational acceleration, and coefficient of friction.