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

["Dan L. MacIsaac" <danmacisaac@mac.com>]

It's actually not so hard to _demonstrate_ Fg attraction with a crude torsion balance built of junk using a VHS tape suspension; the _real_ difficulty is getting good measurements.  I had a student replicate 
http://physicsed.buffalostate.edu/pubs/PHY690/Hughes2009Cavendish/
a balance apparatus described at
http://www.fourmilab.ch/gravitation/foobar/
and videotape quite successfully overcame the endless spinning relaxation you must endure with twine or monofilament.

The student was quite bemused with standing still for about 5min near the apparatus; he could deflect the balance arm with himself.

Dan M

Dan MacIsaac, Associate Professor of Physics, SUNY-Buffalo State College
222SciBldg BSC, 1300 Elmwood Ave, Buffalo NY 14222 USA 1-716-878-3802
<macisadl@buffalostate.edu>  <http://PhysicsEd.BuffaloState.edu>
Physics Graduate Coordinator ON SABBATICAL Fall 2010 / Spring 2011

Fall 2010 Visiting Scholar 
Helsingin yliopisto 224 Physicum, Kumpula Campus 
Gustaf Hällströmin katu 2a FI-00560 Helsinki


On Oct 29, 2010, at 7:00 AM, 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!
>
>
> On 2010, Oct 28, , at 10:39, Bernard Cleyet wrote:
>
> > Yes, and I think credit should be given to Michell who made the beta version of the balance and gave it (indirectly) to C. just before he (Michell) died.
>
>
> cut
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