A fixed pulley carries a weightless thread with masses m_(2) and m_(1) at its ends (m_(2) gt m_(1)). There is friction between the thread and the pulley. If it is such that the thread starts slipping when the ratio of m_(2) to m_(1) is n_(0). Find : (a) the friction coefficient (b) the acceleration of the masses when (m_(2))/(m_(1))=n gtn_(0) [Hint : Consider an element of the thread of width d theta at angular distance theta from the horzontal diameter of the pulley. The forces at the ends are T and T = dT. If dN is the normal reaction of the pulley on the element than df (frictional force on the element) = mu dN Resolving the tensions at the ends along and perpendicular to the radius vector of the element, we have for equilibrium of the element dT = df and dN = T d theta Integrate from T_(1) to T_(2).T_(1)=m_(1)g and T_(2)=m_(2)g. These are obtained by considering equilibriumof m_(1) and m_(2)]