Lenz’s law. A falling magnet changes the magnetic flux through the pipe. The pipe is a conductor, so currents (eddy currents) flow around it in just the direction that opposes the change. Those currents are in the magnetic field of the magnet, so there is a force on them, and an equal and opposite force on the magnet. It always points upwards, against the fall.

EMF ∝ speed, current ∝ conductivity × wall thickness × EMF, braking force ∝ current, so F = kv

Terminal speed. The weight is constant, and the braking force grows with the speed. The magnet speeds up until the two are equal. Then the net force is zero and it falls at a steady speed: mg = kv, so v = mg/k = g/(k/m). Watch the braking force tile climb to 100%.

What changes the braking. A better conductor (copper: 5.9×10⁷ S/m, aluminium: about 3.5×10⁷ S/m, which is 1.7 times less) and a thicker wall both give bigger currents for the same speed, so a bigger k and a lower terminal speed. Plastic is an insulator, so there are no eddy currents and the magnet falls freely.

Flipping the magnet. The currents reverse, but the force does not. The currents always oppose the change, so the braking is exactly the same.

Where the energy goes. The magnet loses gravitational potential energy but does not speed up, so the energy heats the pipe.

The numbers are in relative units, so that you can compare runs. The fall in the plastic pipe is also in slow motion compared with real life.