resistance if we examine the deformation shown in an exggerated manner in the above figure. If force P is along the centreline as shown, the equivalent force system coming onto the roller from the region of contact must be that of a force N whose line of action also goes through the centre of the roller since, you will that three nonparallel forces must be concurrent for equilibrium. In order to develope a resistance to motion, N must be oriented at an angle with the vertical direction, as shown in the above figure. The equations of equilibrium become