Re: [Phys-l] How did Newton estimate the Gravitational constant?

[brian whatcott <betwys1@sbcglobal.net>]

 One of the helpful references in this thread pointed to the Autodesk 
proprietor's science web site.
Though he has the usual boring Republican line on the "Liberal media", 
he shows a splendid setup
 with a step ladder, to which a short length of 6lb rated nylon 
monofilament is tied, secured by a
 bridle to a lath of foam insulation with a lead fishing weight placed 
at each end.
Beneath the lath is fixed a blade of thick aluminum foil cut from a 
cooking tray which dips
in a can of water on the floor  as a damper.

The most esoteric item of the setup, of which he shows time lapse video, 
is the room location
 - a basement store room set in a limestone stratum which provides a 
rather stable temperature.
The experiment is observed with a web cam and a video camera to avoid 
drafts.

The cost might run to $5 plus cameras. He warns that the suspension must 
relax for 2 or 3 days
before it will be stable. (The nylon he used can easily be replaced with 
a stiffer polyester tape
 or VHD polyethylene line or tape, no doubt.)

Brian W

On 10/28/2010 11:00 PM, Bernard Cleyet wrote:
> BTW,  Stong's Amateur Scientist (Sci. Am. Sept. '63)
>
> gives instructions for a Mitchell torsion balance;  it's large -- suspension 55"  (#36 music wire**)  arm, 41" weights (masses) 46 oz. juice can lead filled, and 100 gm.  Both cylindrical -- like the recent rather more accurate one using W.   Spheres are best, but diff. to accurately machine, no?
>
>
>
> **  I remember reading another one using 1/4" mag. tape.
>
> bc notes included an electrostatic shield -- much larger constant!