Aspects concerning the friction for the motion on an inclined plane of an axisymmetric body

The geometrical intrinsic elements defining the Hertzian point contact between two solid bodies are the common normal and the tangent plane in the contact point. To the relative motions occurring about these elements, forces and moments of friction oppose; these reactions are the elements of the friction torsor from contact. The paper presents a particular case when sliding friction and rolling friction coexist in the tangent plane. The first body is made of two identical bearing balls rigidly fastened and the second body is an inclined plane. The straight line defined by the contact points between the mobile body and the plane differs from the steepest line of the plane. By gradually increasing the slope of the plane, the situation when the body simultaneously rolls and slides with respect to the line defined by the contact points is reached. When the duration of motion, the sliding of the centre of mass and the rotation angle of the body between two marks from the plane are measured, it is concluded that the sliding velocity and the angular rolling velocity are independent. While the rotation angle is constant the sliding and time of motion vary in a relatively wide range thus confirm a significant gradient of the coefficients of sliding and rolling friction.