R
Richard Henry
Guest
On Jun 16, 3:58 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
own peril.
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Surveyors and navigators ignore the gravimetric variations at theirOn Wed, 16 Jun 2010 15:36:13 -0700 (PDT), Richard Henry
pomer...@hotmail.com> wrote:
On Jun 16, 12:53 pm, George Herold <gher...@teachspin.com> wrote:
On Jun 16, 2:31 pm, Archimedes' Lever <OneBigLe...@InfiniteSeries.Org
wrote:
On Wed, 16 Jun 2010 11:05:15 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
Cool, I have to scribble numbers on the paper though. 6400 feet is
about 2000m, the Earth is about 6E6 m in radius, Since we only want a
small change I can ignore the r^2 stuff and just multiple the ratio by
2. something like 4 parts out of 6,000. much smaller than the
divisions on your scale.
No you cannot. What makes you think that G decreases (or
increases)linearly?
Big G doesn't change at all. Little g (the force of gravity on the
Earths surface) will go as 1/r^2. For small changes in r the change
is approximately linear... first term in the taylor expansion if you
want to think of it that way. And it does go as 2*delta-R/Rearth
Not exactly. The mass of the Earth is not actually concentrated at a
single point.
Outside of a uniform spherical mass, g does behave as if all the mass
were concentrated at the center. The earth is non-homogenous, but
close enough. The short answer to my little problem is that the change
is about 1 part in 2000, too small to matter in the context of the
other measurement uncertainties.
If something is small enough, we engineers just write it off. A quick,
rough calculation is usually enough to decide if that's safe.
After all the profound word salads and hand-waving about forces and
masses and weights, it was fun to see if the lecturers could do a
simple high-school physics exercize.
John
own peril.