Why do magnets fall more slowly through a copper tube?
When you move a magnet past a metal plate or through a copper tube you generate a current*. Copper isn’t attracted to magnets, but it is very conductive.
If we drop a non-magnetic piece of metal down the copper tube it is unaffected, but in the case of the magnet its movement through the tube generates current. If it stops moving then no current is generated.
This is the same principal that allows the conversion of mechanical energy into electrical energy to charge the headlight on a bike. But why is the magnet moving more slowly?
The current itself generates magnetic fields which oppose the magnetic field generated by the magnet impeding it’s movement.
The key is in explaining that the law* runs both ways; current generates magnetic fields, and magnetic fields generate current.
*This is known as Lenz’s law.