David Billington wrote:
Thanks Chris,

The last time I did this demo was for some friends using magnets
salvaged from some wedding corsage after a wedding I attended in
Holland. The florists had used small NiFeBn magnets taped to the flower
stem and another inside the lapel or dress to hold the flowers in place.
About 10mm diameter and 2mm thick, these were a nice fit in standard
copper tubing, 15mm?, and the increase in time taken to fall compared
to a non magnetic item was quite amazing. I grabbed all the unwanted
corsages and stripped the magnets, although they are not expensive these
days and readily available.

I have maybe 20 small trapezium shaped magnets from 500 MB hard drives.
I'm not certain of the composition, but I think it may be NdFeB. I used
some for a demonstration at a school a couple of years ago. They will
creep down a 3 mm thick aluminium plate inclined at 80 degrees at only a
couple of centimetres per second. The speed in an aluminium tube with 3
mm walls is about the same. You can do some fascinating demonstrations
with these magnets which aren't easily observed with weaker magnets.
They're great fun.

Best wishes,

Chris