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# Re: angular momentum transfer?

After reading (skimming) the replies so far, I agree w/ the later
replies that your memory may be defective, not unheard of here.

I think what you want to demonstrate is conservation of momentum in a
small closed system.

I've described one of my more favoured demos before, and will now bore
the longer time members.

Suspend a large pocket watch on a rigid card (any low mass platform)
using three threads tied to a single one which is hung from a hook.
fasten w/ tacky wax a small mirror on the watch; aim a laser at the
mirror so that it then falls on a far wall. i.e. a light lever. This
will show the watch moving opposite to the motion of the balance wheel
*, roughly showing the conservation of momentum.

* One may remove the back and place the mirror on the platform, so one
may verify (using, say a TV camera) that there is counter rotation.
With the aid of a watchmaker one may determine the mass, etc. and put
some numbers in the mix.

bc

p.s. on a larger scale: sit on a piano stool and rotate a lead weighted
bicycle wheel.

Colin Quinney wrote:

Hello.

I joined yesterday. I am searching for some information. I am a fairly new
student of physics, now retired, and I am presently searching for a
reference to a classroom demo that shows two wheels on a short axle, where
one wheel with lead (Pb) rim is spun up- and another wheel close by (on
the same axle) responds to the momentum change of the first wheel with a
small reverse rotation. I wish to replicate this so that I may study the
phenomena. Neither my text books nor Google however give a reference or
shows this demonstration. I'm confident however that a demo of this sort is
out there somewhere since a retired physics professor originally told me
about it. If anyone could please advise or give a science book reference or
to a correct Google search term, I would be most appreciative. Thanks.

Best Regards,
Colin