find total W.D by fricition assuming plank is sufficiently long.

Find total work done by friction assuming plank is sufficiently long. Solve this question in both ground frame and C-frame.

A plank of mass M rests on a smooth horizontal plane. A sphere of mass m and radius r is placed on the rough upper surface of the plank and the plank is suddenly given a velocity v in the direction of its length. Find the time after which the sphere begins pure rolling, if the coefficient of friction between the plank and the sphere is mu and the plank is sufficiently long.

A liquid wets a solid completely. The meniscus of the liquid in a sufficiently long tube is