“…Unlike Zhuravlev's assumptions, 1,2 we shall assume that the interaction of the sphere with the plane is described by the friction model proposed by Karapetyan. 3,4 , We will assume that e 1 , e 2 , e 3 is a right-handed, orthonormalized moving frame of reference such that the unit vector e 1 is directed along the sliding velocity, u = ue 1 , of the sphere (that is, along the velocity of the point of contact of the sphere with the support plane), the unit vector e 2 is orthogonal to the sliding velocity u and, like e 1 , lies in the horizontal plane, and the unit vector e 3 is directed along the ascending vertical, u s = u + [, ae 3 ] is the velocity of the centre of mass of the sphere and = 1 e 1 + 2 e 2 + 3 e 3 is the angular velocity of the sphere.…”