  We analyze the physics of a type of homopolar motor comprising an AA battery
with two cylindrical neodymium magnets on each end that roll inside a metal
cylindrical tube. The motion of the motor results from the interaction between
the magnetic field of the magnets and the magnetic field created by the current
inside the magnets. We develop a model to describe the dynamics of the system,
including the calculation of the terminal velocity of the motor due to eddy
currents.
