Silly physics...

Björn Lindberg d95-bli at
Wed Feb 12 14:51:37 PST 2003

torsten at (torsten) writes:

> On Wed the 12 Feb 2003 at 13 hours EST
> JC wrote...
> >rbpark-NOSPAM at (Rob Park) writes:
> >
> >> What I'm trying to say, is that the two electrically charged balls were
> >> 3 cm apart, give or take 400,000 km. Note that the moon is less than
> >> 400,000 km away from the Earth. So, we really have no way of being
> >> certain that the little styrofoam balls weren't on the moon...
> >
> >I did a lab in high school where one determines the acceleration due
> >to gravity by swinging a pendulum.  The result should have been 9.8
> >m/s^2, but we got 8.8 m/s^2.  I still don't know what we did wrong.
> >
> >-jc
> Where were you?  Gravity varies exponentially with distance from
> a massive body.  It is only 9.8m/s/s at sealevel.  After that, it
> decreases dramatically.

The increased distance from the earth's core when at an altitude is
still very small compared to the earth radius. At the top of Mount
Everest the gravitational acceleration is maybe about 9.80 m/s^2
instead of 9.82 m/s^2.


War on Iraq, expected # of killed Civilians:
Iraq            500,000
USA                   0
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