  The dynamics of a hollow cylinder containing granules and rolling down an
inclined plane was investigated. A theoretical approach for investigating the
behaviour of such a cylinder was proposed. The critical angle of the plane that
allows the system to roll downward is presented. A simple experiment using six
types of granules consistently confirmed the theoretical predictions. We showed
that the critical angle is independent of the size distribution of the
granules. We observed that the sliding angle of granules inside the cylinder is
constant and, surprisingly, similar to the avalanche angle of the granules. Our
theoretical prediction can be used to determine the critical angle without
considering the shape, surface roughness and size distribution of the granules.
Additionally, we derived the oscillation frequency of the system when it is
slightly deviated from equilibrium, showing the frequency initially increases
and then decreases with increasing granular volume. The oscillation is absent
when the cylinder is empty or fully filled with granules. Furthermore, the
dissipation of energy as a function of the fractional volume and fractional
mass of the cylinder system were determined. This work might help students
understand rolling motions other than the standard rolling motion commonly
taught in the classroom.
