CENTRIFUGAL FORCE - A GEDANKEN EXPERIMENT

A simple gedanken experiment, the motion of a bead inside a rotating l inear pipe, is considered. It is shown that at large enough velocities a centrifugal force acting on the bead changes its usual sign and att racts towards the rotation axis. The motion of the bead is oscillatory , resembling a well-known case of the mathematical pendulum. A possibl e relevance of this highly idealized problem to the real motion of cha rged particles in a pulsar magnetosphere is pointed out.