A piece of string has a heavy flask tied to one end and a rubber stopper tied to the other.  Hang the string over the rod as shown, with the flask a few centimeters below the rod and the stopper end of the string held horizontal.  Release the stopper.  The string will wrap itself around the rod with increasing angular speed and halt the fall of the flask (barring a stopper-flask collision).

Use Mathematica to plot the trajectory.