Date: Thu, 25 Sep 2003 15:46:43 -0700

Author: Doug Johnson

Subject: Re: Motion of falling bodies demo

Post:


I think that Andy Graham has a water drip(bubble?) setup that does the same
thing. The drips are separated by a vibrator on the water tube or
something like that... and as they fall the strobe can make the drips look
like they are falling upward or stopped or go any speed inbetween. I think
it produces a great shadow on the wall too...
Andy, are you out there? Maybe you could shed some more light on this
subject than I. Also, Wayne Peterson at BYU has a large version of this.
If you are interested, I will send you his phone number.

....Doug J.


> I'm trying to recreate an old demo that was used in the 60's that
>is similar to Meiners 7-1.15 (page 115). Basically its an apparatus that
>drops balls at a set rate in synchronization with a strobe. The main
>difficulty is the dispenser--does anyone know of any industrial or
>consumer products that can dispense regular objects at a set rate? Or
>will this have to be custom made...
>
>Gary Steinberg


From dwilley+@pitt.edu Thu Sep 25 17:47:23 2003
Date: Thu, 25 Sep 2003 20:11:48 -0400
From: David Willey
Subject: Re: Motion of falling bodies demo
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This worked for me, hope it helps,
connect a rubber hose to faucet at one end and an a eye-dropper at the other,
clamp the eye-dropper so that it shoots a stream of water in an arch into a
sink or bowl. Run the tube under the arm of a lab vibrator that just uses the
mains' frequency (or set it at 60 hz), set a strobe at 60Hz in front of the
water stream. Put a sheet of black cardboard, with a meter stick taped to it,
behind the parabolic stream of water droplettes, take a picture, analyze.
cheers,
David

Doug Johnson wrote:

> I think that Andy Graham has a water drip(bubble?) setup that does the same
> thing. The drips are separated by a vibrator on the water tube or
> something like that... and as they fall the strobe can make the drips look
> like they are falling upward or stopped or go any speed inbetween. I think
> it produces a great shadow on the wall too...
> Andy, are you out there? Maybe you could shed some more light on this
> subject than I. Also, Wayne Peterson at BYU has a large version of this.
> If you are interested, I will send you his phone number.
>
> ....Doug J.
>
> > I'm trying to recreate an old demo that was used in the 60's that
> >is similar to Meiners 7-1.15 (page 115). Basically its an apparatus that
> >drops balls at a set rate in synchronization with a strobe. The main
> >difficulty is the dispenser--does anyone know of any industrial or
> >consumer products that can dispense regular objects at a set rate? Or
> >will this have to be custom made...
> >
> >Gary Steinberg
From dwilley+@pitt.edu Thu Sep 25 18:20:29 2003
Date: Thu, 25 Sep 2003 20:44:52 -0400
From: David Willey
Subject: Re: Awesome EM induction demo!
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Hi folks,
I recently purchased a 6 inch by 6 inch by 2 inch thick piece of copper,
cooled it down to ln2 temp. and dropped a 1 inch diameter neobium magnet
onto it. I only got a 7 inch drop, any more and the magnet hit the copper.
It's just commercial copper block, cost me $100. I have been reading the
discussion on this but may well have missed something. It's not been
"degassed" or anything, any idea what am I doing wrong here folks? I've got
a bad case of envy here, size does matter ;-)
cheers,
David

From wonnell@pha.jhu.edu Fri Sep 26 05:14:32 2003
Date: Fri, 26 Sep 2003 07:57:58 -0400 (EDT)
From: Steve Wonnell
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Subject: Re: Awesome EM induction demo! (fwd)
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Chuck,

Just to prove the point, a few minutes ago I took a small NeFeB magnet
(1/4" diameter by 1" long, bought from www.wondermagnets.com) and dropped
it on the floor from a height of 5 feet.

It broke in half, one piece flying one way, the other piece flying
another.

Not a lot different from fragile materials.

I stand by my caution.

Steve


On Thu, 25 Sep 2003, Chuck Britton wrote:

> Date: Thu, 25 Sep 2003 19:06:53 -0400
> From: Chuck Britton
> To: Steve Wonnell
> Subject: Re: Awesome EM induction demo!
>
> yes - these NdFeBo magnets WILL break easily. Letting two small disks
> slam together from a coupla inches is enough to break one or both.
>
> BUT - having said that - I have NEVER seen and 'fragments' go flying.
> The various pieces and parts of the previously whole magnet are STILL
> each highly oriented and are VERY quick to reassemble themselves into
> a lower energy configuration.
>
> Has anybody else seen a piece SEPARATE itself from the rest of the magnet???
>
>
> At 4:46 PM -0400 9/25/03, Steve Wonnell wrote:
>
> >Guys and Gals,
> >
> >These NeFeB magnets are under extremely high internal stress.
> >I have a bunch of them that have cracked during storage.
> >
> >I suspect that they crack far more easily than other materials (e.g.
> >steel, or even some ceramics).
>
> --
> Chuck Britton Education is what is left when
> britton@ncssm.edu you have forgotten everything
> North Carolina School of Science & Math you learned in school.
> (919) 416-2762 Albert Einstein, 1936
>


************************************************************************
Steven K. Wonnell
Physics and Astronomy Department E-Mail: wonnell@pha.jhu.edu
Johns Hopkins University Phone: (410) 516-4696, 516-5468
3400 N. Charles Street Fax: (410) 516-7239
Baltimore, MD 21218-2686 Office: 478 Bloomberg
************************************************************************
From Gerald_Zani@brown.edu Fri Sep 26 05:39:30 2003

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