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Re: falling magnet demo



I must tell a story on myself about the "Falling Magnet Demo." When I
first did this experiment (fortunately without students present) I use a
metal clamp to hold the rod. When I dropped the "cow magnet" through the
tube, it never did come out the bottom. I got a good laugh in private.

L. Herr

Project PHYSLab
The Catlin Gabel School
Portland, OR 97225
On Mon, 10 Mar 1997, Roger A. Pruitt wrote:

On Mon, 10 Mar 1997, JFDWG wrote:

I tried a classic demonstration of dropping a magnet through a copper
tube at the same time as dropping an unmagnetized bar. They both
landed at the same time.

I think this demo is normally done with neodymium supermagnets. The
magnet should be a stubby rod in shape, with only a small clearance around
the tube, a "slip-fit" in other words.

.....................uuuu / oo \ uuuu........,.............................
William Beaty voice:206-781-3320 bbs:206-789-0775 cserv:71241,3623


In a previous note, I pointed out that our "tube" is made of four or five
nested copper pipes about 2.5 m long. Our magnets are "cattle" magnets about
3" long purchased from a local farm supply store. They are small cylindrical
steel magnets of much lower cost and strength than neodymium. Our machinist
also fashioned a similar cylindrical piece of nonmagnetized soft iron. We
drop this through the tube for comparison with the magnet's fall time. It
also dispels the notion that friction slows the magnet's fall.

Roger