A popular classroom demonstration of Lenz’s law involves a vertical copper tube and a permanent magnet that fi ts very loosely inside the tube. The instructor fi rst shows that a permanent magnet is not attracted to the copper. The magnet is then dropped down the tube and takes a surprisingly long time to come out the bottom end of the tube. When repeating the demonstration, a student looks down the tube and sees that the magnet actually moves at a constant and rather slow velocity and does not come in contact with the tube. Explain how this demonstration illustrates Lenz’s law. Why doesn’t the magnet come to a complete stop?