A Solid sphere is rolling purely on a rough horizontal surface ( Coefficient of kinetic friction = μ) with speed of centre = V. It collides inelastically with a smooth vertical wall at a certain moment, the coefficient of restitution being $\frac{1}{2}$. The sphere will begin pure rolling after a particular time which can be expressed in form of $\frac{aV}{bμg}$ where a and b are co-prime.