Final answer:
A bar magnet dropped in a copper pipe falls slowly due to electromagnetic induction, which causes eddy currents that produce a magnetic field opposing the magnet's motion.
Step-by-step explanation:
If you drop a bar magnet in a vertical copper pipe, it will fall slowly not because of air resistance, but because as the magnet moves through the pipe, it induces an electric current in the copper. Since copper is a good conductor of electricity, these currents, known as induced currents or eddy currents, will flow in such a way as to create a magnetic field that opposes the motion of the bar magnet. According to Lenz's Law, which is a part of electromagnetic induction, the direction of induced current in a circuit is such that it creates a magnetic field that opposes the change in magnetic flux that induced it. In the case of dropping a bar magnet through a copper tube, the currents induced will thus create a magnetic field that resists the magnet's motion, causing it to fall more slowly than it would under the influence of gravity alone.