Re: "simple" Newtonian mechanics question

From: Franz Heymann (notfranz.heymann_at_btopenworld.com)
Date: 02/18/05 

Date: Fri, 18 Feb 2005 22:06:39 +0000 (UTC)

"Captain Crunch" <fqmj-s3ph@dea.spamcon.org> wrote in message
news:8ejc11dqdpu7v46nclvjl9o7rjesunv66i@4ax.com...
> I hold an undergraduate degee in physics, but was stumped by a
> "simple" mechaics problem my son recently asked me. Maybe someone
here
> can help me with his comments about this matter:
>
> My son asked me, "How much would a 1 kg mass weigh at the bottom of
a
> well shaft 1000 km deep? I can see that if the well shaft went all
the
> way to the Earth's center, it'd weigh nothing there. It seems as
> though his problem's analysis is too complex for me. To solve it, I
> would not only have to compute the gravitational attaction of the
> Earth's portion below 1000 km, a simple problem, but also the
> gravitational attaction of its spherical shell above 1000 kms on an
> object not at the center, impossibly complicated, it seems! Can
anyone
> here comment about this problem?

Assuming a homogeneous spherically symmetrical earth, the shell above
the bottom of the well contributes nothing.
The full result is that g varies directly proportionally to r, until
the surface is reached, after which it decreases as r^-2 

-- 
Franz
"As we grow older we understand more and more and we do less and less"
Puppi

Relevant Pages

  • Re: Pushrod Woes
    ... This can cause trim and in-flight changes to control surface ... I've already conceded that the materials may flex under load. ... In my pattern planes and my gasoline-powered planes, ...
    (rec.models.rc.air)
  • Re: Pushrod Woes
    ... This can cause trim and in-flight changes to control surface movement. ... In my pattern planes and my gasoline-powered planes, ... For planes like a Q-Tee, Whimpy, or the average 20 to 40 size trainer, Nyrods are great. ... That's become my default pushrod on most of what I build. ...
    (rec.models.rc.air)
  • Re: Ultra compact
    ... I am looking for an ultra compact camera for a gift, ... view finder (and LCD monitor as well), not the one with LCD monitor only. ... Also, I am excluding cameras using Memory stick in a different flavors (duo, ...
    (rec.photo.digital)
  • Re: "simple" Newtonian mechanics question
    ... >can help me with his comments about this matter: ... >well shaft 1000 km deep? ... I can see that if the well shaft went all the ... >would not only have to compute the gravitational attaction of the ...
    (sci.physics)
  • Re: MOXI DVR storage enlargement via USB hard drive
    ... With the hi def programs I get about 8 hours max. ... MOXI DVR? ... The USB ports are reserved for the new HD units coming out later this ... The cable companies will be updating the the guts standard def units ...
    (alt.tv.tech.hdtv)