  The motion of a hoop hung on a spinning wire provides an illustrative and
pedagogical example of a supercritical bifurcation. Above a certain angular
velocity threshold Omega_c, the hoop rises, making an angle theta =
(Omega-Omega_c)^(1/2) with the vertical. The equation of motion is derived in
the limit of a long massless wire, and the calculated steady states are
compared to experimental measurements. This simple experiment is suitable for
classroom demonstration, and provides an interesting alternative to the
classical experiment of the bead sliding on a rotation hoop.
