  We analyse a mechanical system in two-dimensional relative motion with
friction. Although the system is simple, the peculiar interplay between two
kinetic friction forces and gravity leads to the wide range of admissible
solutions exceeding most intuitive expectations. In particular, the strong
qualitative dependence between behaviour of the system, boundary conditions and
parameters involved in its description is emphasised. The problem is intended
to be discussed in theoretical framework and might be of interest for physics
and mechanics students as well as for physics teachers.
