Several studies have showed the subsistence, even in students enrolled in scientific degree courses,
of spontaneous ideas regarding the motion of bodies that conflict with Newton’s laws. One of the
causes is related to the intuitive preconceptions that students have about the role of friction as a
force. In fact, in real world novices do not recognise friction as a force, and for this reason they
may believe that a motion with a constant speed needs as a necessary condition the presence of a
constant force in the same direction of the motion. In order to face these ‘intuitive ways of
reasoning’, in this paper we propose two sequential experiments that can allow undergraduate
students to clarify the role of friction forces through the use of the work–energy theorem. This is
a necessary first step on the way to a deeper understanding of Newton’s second law. We have planned
our experiments in order to strongly reduce quantitative difficult calculations and to facilita…