Re: curvature of buckets of water

[Bob Sciamanda <trebor@VELOCITY.NET>]

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)