So it's the mass of the fluid that is displaced by that particle. So we're going to designate that as M. This where this is displaced and it's multiplied by the acceleration, which is once again omega squared multiplied by R. Now, what is the force? Frictional. Well, the Force frictional is simply equal to the coefficient multiplied by the velocity of that object. So we have the frictional force is equal to the coefficient of friction multiplied by the velocity of that object. So these three forces are given by the following three equations.