Re: curvature of buckets of water

[Herbert H Gottlieb <herbgottlieb@JUNO.COM>]

Hi Bob.....

And another good one is to place a tub of hot melted paraffin on a
rotating
turntable. When it cools and solidifies its parabolic surface can be
used to make good mirrors for physics demos or telescopes.

Anyone else want to add to this list of demos on  turntables??

Herb Gottlieb

On Sun, 04 Jul 1999 15:59:21 -0400 Bob Sciamanda <trebor@VELOCITY.NET>
writes:
> Hi, Herb!
>    It was about the same time (the 60's?) when I saw a large rotating
> tub
> (diam=c. 6ft.) of dirt with growing saplings (c. 5 ft. high) at the
> Ontario Science Center.  They also knew their physics and were
> markedly
> inclined toward the center.
> I have demo'd this effect with candle flames (covered to eliminate
> wind
> effects), helium balloons and floating bobs tethered to the bottom of
> a
> bottle of water, all (in turn) fastened to the ends of a horizontal
> 2x4
> spun slowly by hand about a vertical axis through its center.  One
> can
> begin by first putting the 2x4 into translational acceleration and
> then
> asking for a prediction of the rotational results.
> Of course the helium balloon tethered to the floor of an accelerating
> car
> (contrasted with a plumb line hanging from the ceiling) is a standard
> puzzler to put to an intro class; many will not believe the predicted
> results until they actually see one of the above demos.  As already
> noted,
> best advantage is taken of these demos by analyzing them both with
> and
> without the Equivalence Principle.
>
> -Bob
>
> Bob Sciamanda
> Physics, Edinboro Univ of PA (em)
> trebor@velocity.net
> http://www.velocity.net/~trebor
>
>
> ----- Original Message -----
> From: Herbert H Gottlieb <herbgottlieb@JUNO.COM>
> To: <PHYS-L@LISTS.NAU.EDU>
> Sent: Sunday, July 04, 1999 10:07 AM
> Subject: Re: curvature of buckets of water
>
>
> > The spinning bucket reminds me of a nice corridor display that I
> saw
> > at Lake Forest College about 35 years ago.
> >
> > Grow some grass seed on a phonograph turntable. After a few
> > days, the seeds will germinate and the grass blades will all
> > slant to the center of the turntable instead of growing vertically
> erect.
> > Herb Gottlieb from New York City
> > (Where we enjoy fooling Mother Nature's planned geotropism)