It would take about 3 to 8 seconds for it to fall through the pipe. As the neodymium magnet falls through the pipe. It's strong magnetic field generates an electric current within the pipe called, Eddy Current. That, in turn, produces a repulsion force against the magnet which creates a dynamic braking action. This is why the magnet falls slowly through the copper pipe.
Copper conducts electricity better than aluminum does.
This can be bought at home centers. A small neodymium magnet which fits in the channeling. You will also need a piece of aluminum, the same size as the magnet. To do this experiment, hold the L-channeling with the bottom of the V side down at an angle of 45 degrees or a little steeper. Start with a piece of aluminum, place it in the channel at the top and let it go.