AB is a non uniform plank of length `L = 4R` with its centre of mass at C such that `AC = R`. It is placed on a step with its one end A supported by a cylinder of radius R as shown in figure. The centre of mass of the plank is just outside the edge of the step. The cylinder is slowly rolled on the lower step such that there is no slipping at any of its contacts. Calculate the distance through which the centre of the cylinder moves before the plank loses contact with the horizontal surface of the upper step.

Answer

R