| |
 |
|
|
Science Forum Index » Physics Forum » Gravitation and the equatorial bulge
Page 1 of 1
|
| Author |
Message |
| Gerrit |
 Posted: Tue Mar 02, 2004 10:37 am |
|
|
|
Guest
|
Hello,
the Earth bulges near the equator, so the equator is located further
from the center of mass than the poles. Why then doesn't water flow
north, towards the point that is located closest to the earth's center
of mass? Doesn't gravity pull water (and anything else) it that way?
yours,
Gerrit.
(Yes, this question is actually from a Physics textbook in slightly
other words, but it's not a homework assignment and the answer is not
included  |
|
|
| Back to top |
|
| Gregory L. Hansen |
| Posted: Tue Mar 02, 2004 11:01 am |
|
|
|
Guest
|
In article <slrnc49s3u.67u.gerrit@localhost.localdomain>,
Gerrit <gerrit@nl.linux.org> wrote:
Quote: Hello,
the Earth bulges near the equator, so the equator is located further
from the center of mass than the poles. Why then doesn't water flow
north, towards the point that is located closest to the earth's center
of mass? Doesn't gravity pull water (and anything else) it that way?
yours,
Gerrit.
(Yes, this question is actually from a Physics textbook in slightly
other words, but it's not a homework assignment and the answer is not
included
Water doesn't flow towards the poles for the same reason that the rest of
the bulge doesn't flow towards the poles.
You can create an impromptu model of this: hawk a lugi in the air. You'll
probably get spinning dumbbells more often than not, but the
generalization to a slow rotation should be pretty easy to figure out.
--
"Things should be made as simple as possible -- but no simpler."
-- Albert Einstein |
|
|
| Back to top |
|
| Franz Heymann |
| Posted: Tue Mar 02, 2004 12:00 pm |
|
|
|
Guest
|
"Gerrit" <gerrit@nl.linux.org> wrote in message
news:slrnc49s3u.67u.gerrit@localhost.localdomain...
Quote: Hello,
the Earth bulges near the equator, so the equator is located further
from the center of mass than the poles. Why then doesn't water flow
north, towards the point that is located closest to the earth's center
of mass? Doesn't gravity pull water (and anything else) it that way?
And centrifugal force restores the equilibrium
Franz |
|
|
| Back to top |
|
| Greg Neill |
| Posted: Tue Mar 02, 2004 4:17 pm |
|
|
|
Guest
|
"Gerrit" <gerrit@nl.linux.org> wrote in message
news:slrnc49s3u.67u.gerrit@localhost.localdomain...
Quote: Hello,
the Earth bulges near the equator, so the equator is located further
from the center of mass than the poles. Why then doesn't water flow
north, towards the point that is located closest to the earth's center
of mass? Doesn't gravity pull water (and anything else) it that way?
DAGS: Geoid
Is your Earth spinning just like ours? |
|
|
| Back to top |
|
| Uncle Al |
| Posted: Tue Mar 02, 2004 5:14 pm |
|
|
|
Guest
|
Gerrit wrote:
Quote:
Hello,
the Earth bulges near the equator, so the equator is located further
from the center of mass than the poles. Why then doesn't water flow
north, towards the point that is located closest to the earth's center
of mass? Doesn't gravity pull water (and anything else) it that way?
The reason is grvity vs. gravitation. At all points at Earth's sea
surface gravity is normal to the surface, whereas gravitation (what
something in orbit feels) is radial. There is no contradiction here.
All points *on the Earth's surface* experience centripetal as well as
gravitational accelerations. They sum to gravity. The Earth' surface
is shaped to allow/enforce the normality to the seas' surface of
gravity.
The Tibetan Plateau, the Andes, etc., distort the direction of local
gravity.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net! |
|
|
| Back to top |
|
| Richard Henry |
| Posted: Tue Mar 02, 2004 5:51 pm |
|
|
|
Guest
|
"Gerrit" <gerrit@nl.linux.org> wrote in message
news:slrnc49s3u.67u.gerrit@localhost.localdomain...
Quote: Hello,
the Earth bulges near the equator, so the equator is located further
from the center of mass than the poles. Why then doesn't water flow
north, towards the point that is located closest to the earth's center
of mass? Doesn't gravity pull water (and anything else) it that way?
yours,
Gerrit.
(Yes, this question is actually from a Physics textbook in slightly
other words, but it's not a homework assignment and the answer is not
included
Gravity is not the only "force" involved. |
|
|
| Back to top |
|
| GR_Learner@GR.grv |
| Posted: Wed Mar 03, 2004 1:57 pm |
|
|
|
Guest
|
"Gerrit" <gerrit@nl.linux.org> wrote in message
news:slrnc49s3u.67u.gerrit@localhost.localdomain...
Quote: Hello,
the Earth bulges near the equator
An oblate spheroid, yes.
Quote: , so the equator is located further
from the center of mass than the poles.
For an isotropic spheroid, yes.
Quote: Why then doesn't water flow
north, towards the point that is located closest to the earth's center
of mass?
How do you know it would not for a perfectly smooth oblate spheroid? Oh...
right... the real world.
Things to consider:
Variations of density at various points on and in the oblate spheroid.
Spinning.
Friction.
Non-smooth surface.
Quote: Doesn't gravity pull water (and anything else) it that way?
The oblatenes of the earth is to first order caused by the spin of the
planet on its axes. Then there are other effects to consider, like variable
density, elasticity etc. However, let us assume that we have a blob of
elastic material that is spinning on axes, and is homogeneous and isotropic.
The surface formed under the rotation will be the oblate spheroid, and
represents a minimization of surface with respect to the forces acting on
the blob. This means that the surface is a eqi-potential. From your basic
physics text, what does an equipotential mean with respect to a
gravitational field? What is the work done moving a particle from pone
point on an equipotential to another point?
Quote: yours,
Gerrit.
(Yes, this question is actually from a Physics textbook in slightly
other words, but it's not a homework assignment and the answer is not
included |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Wed Dec 03, 2008 8:51 pm
|
|