If an induced current flows, its direction is always such that it will oppose the change which produced it.

A magnet is dropped down a conducting copper pipe and produces a force that opposes its motion down the tube. The falling magnet induces a current in the copper pipe, by Lenz's Law, the current creates a magnetic field that opposes the changing field of the falling magnet. Thus, the magnet is "repelled" and falls more slowly

What is the relationship between the thickness of the aluminium pipe and the rate at which a magnet falls through it?

Purchase aluminium foil of different lengths, as shown on the right.

Measure the thickness of the aluminium foil wrapped around the cardboard tube.

Why is it necessary to make sure the internal diameter of the cardboard tube is the same?
Formulate a hypothesis?