Consider the system shown in the figure. A rope goes over a pulley. A mass, \( m \), is hanging from the rope. A spring of stiffness, \( k \), is attached at one end of the rope. Assume rope is inextensible, massless and there is no slip between pulley and rope.

The pulley radius is \( r \) and its mass moment of inertia is \( J \). Assume that the mass is vibrating harmonically about its static equilibrium position. The natural frequency of the system is