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. And now in step two, we basically want to replace all these forces with the right side of these equations. So this becomes we have m omega squared r minus in parentheses. We have misplaced multiplied by omega squared r plus this quantity here.