Date: Tue, 30 Sep 2003 16:24:23 -0400

Author: Wolfgang Rueckner

Subject: Re: gravity

Post:

Dick -- they've used many many techniques over the years. Yes, I
would think that the location of the g measurement is "plumb" with
the COM of the apparatus. Recent measurements are performed with
laser interferometric techniques on dropping objects in a vacuum.
The most recent I've read about utilizes two satellites in the same
orbit. One is following the other (within direct sight) and measures
the distance between them (again, interferometrically) to some
incredible precision. As the first satellite goes over a part of the
earth where g changes, the distance between the two satellites
changes, and that change is used to calculate g. -- Wolfgang

>Wolfgang,
>
>Then Gary's quote for Bergen should be at 38.00 meters? What does it
>really mean to have g to so many figures? What kind of apparatus is small
>enough to locate it to such a tolerance, or is that the center of mass of
>the apparatus????
>
>Dick Berg
>
>On Tue, 30 Sep 2003, Wolfgang Rueckner wrote:
>
>> >I'm trying to find a "simple" listing of the local gravity in worldwide
>> >cities, specifically Oslo, Norway. I've searched the net, but only came up
>> >with gravity tables of longitude and elevation for the US (no specific
>> >cities). A few textbooks list some cities. I am trying to compile a list
>> >of cities around the world to compare ranges for projectiles (Olympic
>> >events) in my class. Can anybody help?
>>
>> I would try the Charles Stark Draper Laboratory in Cambridge MA (my
>> fair city) which specializes in such things. Wolfgang
>>
>> BTW, in my 1987 AJP paper (an accurate determination of the
>> acceleration of gravity for lecture hall demonstration), I quoted a
>> value of g for this local (980.386775 cm/s^2) given to me by the
>> Draper Lab. Note that the number of significant figures implies a
>> sensitivity of +- 3mm in altitude!
>>
>>
>
>***********************************************************************
>Dr. Richard E. Berg, Professor of the Practice
>Director, Physics Lecture-Demonstration Facility
>U.S. mail address:
>Department of Physics
>University of Maryland
>College Park, MD 20742-4111
>Phone: (301) 405-5994
>FAX: (301) 314-9525
>e-mail reberg@physics.umd.edu
>www.physics.umd.edu/lecdem
>***********************************************************************
From peacock@physics.utah.edu Tue Sep 30 13:45:50 2003
Message-ID: <3F79E87B.78E36276@physics.utah.edu>
Date: Tue, 30 Sep 2003 14:32:59 -0600
From: "Zigmund J. Peacock"
Organization: University of Utah , Department of Physics
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Subject: Re: Van de Graaff
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Paul, your bottom roller needs to be covered with a wool fabric, it
should cure you weak charges blues. Zig

Jerry DiMarco wrote:

> At 10:54 AM 9/26/2003, you wrote:
>
>> ...But the VDG still does not generate much charge - and as it stays
>> on for a
>> couple minutes the charge decreases - so it might be leaking
>> somewhere?
>> I replaced the disintegrated cloth on the bottom roller with what I
>> think is
>> an acrylic/polyester cloth. I think the two rollers need to be
>> different
>> materials - hence the cloth, is that right? What should the cloth
>> be, or do
>> I even need it?
>
Zigmund J. Peacock
WWW.physics.utah.edu/people/staff/peacock.html
University of Utah/Physics peacock@physics.utah.edu
115 SOUTH 1400 EAST #201 Tel 801 581 6602
SALT LAKE CITY UT 84112-0830 Fax 801 581 4801

"We sleep safely in our beds because rough men stand ready in
the night to do violence to those who would do us harm"
-- George Orwell

"All that is necessary for the triumph of evil is that good
men do nothing!"
-- Edmund Burke


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Paul, your bottom roller needs to be covered with a wool fabric, it should
cure you weak charges blues. Zig

Jerry DiMarco wrote:

At 10:54 AM 9/26/2003, you wrote:
...But the VDG still does not generate
much charge - and as it stays on for a

couple minutes the charge decreases - so it might be leaking somewhere?

I replaced the disintegrated cloth on the bottom roller with what I
think is

an acrylic/polyester cloth. I think the two rollers need to be different

materials - hence the cloth, is that right?  What should the cloth
be, or do

I even need it?


Zigmund J. Peacock          
WWW.physics.utah.edu/people/staff/peacock.html

University of Utah/Physics                  
peacock@physics.utah.edu

115 SOUTH 1400 EAST #201                    
Tel 801 581 6602

SALT LAKE CITY UT 84112-0830                
Fax 801 581 4801

 "We sleep safely in our beds because rough men stand ready in

the night to do violence to those who would do us harm"

        -- George Orwell

 "All that is necessary for the triumph of evil is that good

men do nothing!"

         -- Edmund Burke

 

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From dwilley+@pitt.edu Tue Sep 30 14:09:31 2003
Date: Tue, 30 Sep 2003 16:52:49 -0400
From: David Willey
Subject: Re: Inertia Ball
In-reply-to:

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This will work with any large mass. Pull hard and quick, the bottom
string breaks, pull very slowly the top string breaks. Science
kit/Boreal labs (among others) sells balls for this #66414-00 pg 616 of
the 2003 catalog price $32.50 (you'll need two)
cheers
David

George M. Caplan wrote:

>Sam writes:
>
>Can you describe the demo?
>
>Thanks,
>
>Sam
>*********
>A large cylindrical mass is supported by a string.
> Another similar string is tied to the bottom of the mass.
>The whole thing is in a "frame".
>The "operator" pulls *with two hands" on a rod tied to the lower string.
>
>George
>
>
>
From dimarco@physics.montana.edu Tue Sep 30 14:10:07 2003

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