If we drop a magnet through a copper pipe (without it touching any of
the sides), it would fall slower than it would if there were no pipe.
The simple answer to this would be because there's a flux of magnetic field lines around the magnet.
So as they say there is an induction in the pipe which makes its upper end to gain the same polarity as the magnets lower end falling towards the coil, that creates a repulsion slowing the magnet down.
That is because of the fact that when flux changes through the pipe, it creates an electric field in the conduction and when charges move along electric field lines work is done on them, whether it involves storing potential energy (negative work) or increasing kinetic energy (positive work).
When net positive work is applied to a charge q1, it gains speed and momentum. The net work on q1 thereby generates a magnetic field whose strength (in units of magnetic flux density (1 tesla = 1 volt-second per square meter)) is proportional to the speed increase of q1. This magnetic field can interact with a neighboring charge q2, passing on this momentum to it, and in return, q1 loses momentum.
The charge q2 can also act on q1 in a similar manner, by which it returns some of the momentum that it received from q1. This back-and-forth component of momentum contributes to magnetic inductance. The closer that q1 and q2 are, the greater the effect. When q2 is inside a conductive medium such as a thick slab made of copper or aluminum, it more readily responds to the force applied to it by q1. The energy of q1 is not instantly consumed as heat generated by the current of q2 but is also stored in two opposing magnetic fields
But, why is there even any interaction between the pipe and magnet in
the first place? Why can't there just be zero interaction? This way,
the magnet is only affected by gravity, just how it would be if it
were just a normal wooden or plastic pipe!
Its simply because there are invisible field lines acting to oppose the motion.
So for example : when you hold two bar magnet's , they repel or attract, right ?
But you never asked why can there be no interaction, just like holding a two wood logs does nothing.
But that's ridiculous because magnetic force makes them do so. That's the same thing happening here.