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Hugh Clary · Guest

I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!

Hugh

Ray Vickson · Guest

On Jul 21, 7:55 am, Hugh Clary <badin...@netzero.ZAPTHISnet> wrote:
[quote]I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?
[/quote]
So much depends on what you know already, and we have no way to judge
that.

If you cannot follow any of the explanations given in your link above,
the best idea is to get a Physics 101 textbook and read the chapter on
angular momentum. It will have several explanations, probably ranging
from the informal to the formal, and will likely be replete with
simple illustrative examples, followed, perhaps, by several not-so-
simple examples. The internet is not always the best learning
resource. Possibly, however, you can find free on-line versions of
course notes or textbooks, so you could read those if going to the
library or the bookstore is not appealing to you for some reason.

R.G. Vickson

[quote]
Appreciate it!

Hugh[/quote]

Sue... · Guest

On Jul 21, 10:55 am, Hugh Clary <badin...@netzero.ZAPTHISnet> wrote:
[quote]I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!
Chapter 4. Conservation of Angular Momentum[/quote]
Section 4.1 - Angular Momentum in Two Dimensions
Section 4.2 - Rigid-Body Rotation
Section 4.3 - Angular Momentum in Three Dimensions
http://www.lightandmatter.com/html_books/0sn/ch04/ch04.html

http://www.google.com/search?hl=en&q=%22angular+momentum%22+elipse+rigid&btnG=Google+Search

Sue...

[quote]
Hugh[/quote]

Puppet_Sock · Guest

On Jul 21, 10:55 am, Hugh Clary <badin...@netzero.ZAPTHISnet> wrote:
[quote]I am looking for an understandable definition
of angular momentum.
[snips]
Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?
[/quote]
How>s this?

http://en.wikipedia.org/wiki/Angular_momentum

Plus, why on Earth are you expecting the `net to provide
you with quality explanations of such concepts? The net
is full of just about every kind, form, and shape of human
that exists. You get corresponding types of responses.

Get a textbook. Angular momentum is usually first taught
in highschool, round about age 16 or so. Get a highschool
physics text. Read it. Do the homework questions. If you
have specific questions about that work, come back and ask.
Socks

Androcles · Guest

"Hugh Clary" <badinage@netzero.ZAPTHISnet> wrote in message
news:4885a2e8.6123500@news.individual.net...
|I am looking for an understandable definition
| of angular momentum. Definitions abound on
| the internet, but they are all incomprehensible,
| at least to me:
|
| http://tinyurl.com/5tfaxf
|
| Beyond that, apparently the planets Jupiter and
| Saturn possess some 90% of our solar system>s
| angular momentum, all by themselves.
|
| Can anyone explain these concepts to me, hopefully
| in terms that my admittedly poor comprehensive
| abilities can follow?
|
| Appreciate it!
|
| Hugh

On the page you cite we see
"For a particle, the cross product of the vector from a specified
reference point to the particle and the particle>s linear momentum".

This assumes you know what a vector is, what a cross product is,
what a specific reference point is, what linear momentum is.

That>s a prerequisite to understanding the terminology (or jargon if
you prefer) and something you have to learn just as a truck driver
has to learn what a "fifth wheel" is, but does little to help you with
an intuitive notion of the meaning of the term "angular momentum".
When an ice skater spins on a "specific reference point"
(watch the movie) http://www.bsharp.org/physics/stuff/skater.html
his/her mass doesn>t change, but the rate of spin DOES change
as he or she brings her arms in or moves them out. However,
his/her angular momentum remains constant. That is very useful
to an engineer designing one of these:
http://www.history.rochester.edu/steam/thurston/1878/f29p115.gif
because it controls the steam and regulates the speed of the engine,
and he needs to know what the RPM will be, what mass to make
the balls that fly out and how far they>ll rise.
Stating that Jupiter and Saturn (two different planets with two
different angular velocities) possess some 90% of our solar
system>s angular momentum the specific reference point being
the Sun) isn>t particularly useful to anyone, its the kind of meaningless
crap a schoolteacher wants to say to impress his students and inflate
his own ego. The planets are the largest so of course they have most
of the angular momentum. Big hairy deal.

Dirk Van de moortel · Guest

Androcles <Headmaster@Hogwarts.physics> wrote in message
%w2hk.14821$%F3.12495@newsfe27.ams2
[quote]"Hugh Clary" <badinage@netzero.ZAPTHISnet> wrote in message
news:4885a2e8.6123500@news.individual.net...
I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!

Hugh

On the page you cite we see
"For a particle, the cross product of the vector from a specified
reference point to the particle and the particle>s linear momentum".

This assumes you know what a vector is, what a cross product is,
what a specific reference point is, what linear momentum is.
[/quote]
.... which differs rather wildly from what Androcles thinks it is:
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/IdiotVectors.html
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/AndroVec.html
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/VectorLength.html
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/VectorSpaces.html

Welcome to learning from crackpots on the net :-)

Dirk Vdm

Cwatters · Guest

"Hugh Clary" <badinage@netzero.ZAPTHISnet> wrote in message
news:4885a2e8.6123500@news.individual.net...
[quote]I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:
[/quote]
It>s the reluctance of an object to start or stop _rotating_.

Experiment with a bike wheel or roundabout at the kids park.

[quote]http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.
[/quote]
because those two account for most of the mass of the planets in the system.

ok it>s not quite that simple but that>s good enough for starters. The
distance of the mass from the center and the speed of rotation is also
important.

Igor · Guest

On Jul 21, 12:26 pm, "Dirk Van de moortel" <dirkvandemoor...@ThankS-NO-
SperM.hotmail.com> wrote:
[quote]Androcles <Headmas...@Hogwarts.physics> wrote in message

%w2hk.14821$%F3.12...@newsfe27.ams2

"Hugh Clary" <badin...@netzero.ZAPTHISnet> wrote in message
news:4885a2e8.6123500@news.individual.net...
I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!

Hugh

On the page you cite we see
"For a particle, the cross product of the vector from a specified
reference point to the particle and the particle>s linear momentum".

This assumes you know what a vector is, what a cross product is,
what a specific reference point is, what linear momentum is.

... which differs rather wildly from what Androcles thinks it is:
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/IdiotVectors.html
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/AndroVec.html
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/VectorLength.html
http://users.telenet.be/vdmoortel/dirk/Physics/Fumbles/VectorSpaces.html

Welcome to learning from crackpots on the net :-)

Dirk Vdm
[/quote]
Ah, the wonders of psycho-ceramics never cease.

Timberwoof · Guest

In article
<5a8e9fe2-79e2-426c-968d-0118669d5c34@f63g2000hsf.googlegroups.com>,
Puppet_Sock <puppet_sock@hotmail.com> wrote:

[quote]On Jul 21, 10:55 am, Hugh Clary <badin...@netzero.ZAPTHISnet> wrote:
I am looking for an understandable definition
of angular momentum.
[snips]
Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

How>s this?

http://en.wikipedia.org/wiki/Angular_momentum
[/quote]
Unfortunately, the first paragraph is enough to make anyone unfamiliar
with vectors scream and run away. Someone who knows all the required
linear algebra to understand that definition probably already
understands angular momentum. There are some slightly better definitions
in the Discussion section, although they have their own criticisms. It
seems that no one has gone to the trouble of writing a definition in
English that is at once comprehensible without advanced mathematics and
correct.

[quote]Plus, why on Earth are you expecting the `net to provide
you with quality explanations of such concepts? The net
is full of just about every kind, form, and shape of human
that exists. You get corresponding types of responses.
[/quote]
I enjoyed reading Androcles' posts on the subject, but not in the same
way I enjoy reading Scientific American.

[quote]Get a textbook. Angular momentum is usually first taught
in highschool, round about age 16 or so. Get a highschool
physics text. Read it. Do the homework questions. If you
have specific questions about that work, come back and ask.
Socks
[/quote]
Yep. That>s the best way.

Hugh, angular momentum is the tendency of rotating things to go on
rotating, not only at the same speed but around the same axis.

There was a good introductory definition on
http://topex.ucsd.edu/erth01/Glossary.html
Angular momentum: A measure of an object>s tendency to keep rotating
and to maintain its orientation. Mathematically it depends on the
object>s mass, m, radius, r, and rotational velocity, v, and is
proportional to mvr. The tendency of a rotation body to continue
rotating; mathematically, the product of mass, velocity and radius. A
measure of the momentum associated with rotational motion about an axis.

What it all comes down to is that the best shape to store rotational
energy is a wheel with thin spokes and a fat outer surface. Also, if you
try to turn a wheel that>s rotating, weird things will happen to the
thing>s rotational axis. Go remove the front wheel from your bicycle.
Hold it out at arm>s length, one end of the axle in each hand, and set
it spinning. Now try to twist the axle sideways. The wheel will wobble
in some fun ways what will have every delicate glass object within
striking distance quivering in fright. That will give you a very good
intuitive notion of the concept. The math to describe what>s happening
is more complicated...

--
Timberwoof <me at timberwoof dot com> http://www.timberwoof.com
Official naysayer of the DARPA kind, who knows only of what¹s accepted by
the Old Testament of the Zionist/Nazi New World Order
which refuses to accept or allow deductive reasoning.

PD · Guest

On Jul 21, 9:55 am, Hugh Clary <badin...@netzero.ZAPTHISnet> wrote:
[quote]I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!

Hugh
[/quote]
Other people have pointed out that the best way to learn about things
like this is in live conversation with someone who knows about it.
That way, it can be put in a context that is meaningful to you.

It also depends on how much you understand linear momentum.

Here are some facts skirting around what momentum is:
1. It is remarkable that there are some quantities that can be defined
and measured in physics that turn out to be constants for a system (a
group of physical objects), no matter what happens inside the system.
This turns out to be useful, because if you know what that number is
for a system before things start happening inside, then *no matter
what* happens after that point, you have at least one constraint on
how things will end up, because this number will end up being the
same, even if the final configuration of the system is the same. When
such a quantity is discovered, the fact that it remains constant for a
system is what we mean when we say it is "conserved" and the law that
says it is always constant is call a conservation law, like the "law
of conservation of momentum".
2. Some of these numbers are identified just by a number and units
(like 37 kW-hrs) and the jargon term for that is "scalar". Some of
these numbers are identified by a number and units and a direction
(like 4.28 kg-m/s in a direction 8 degrees east of vertically upward),
and the jargon term is "vector". Energy is a conserved scalar
quantity. Momentum is a conserved vector quantity.
3. It turns out that you can define a unique direction for angular
momentum, even though the motion may be rotation in a circle. You
might think this means all directions, by the time you get all the way
around in a circle, or at least a constantly changing direction, but
the direction of angular momentum is typically (not always) along the
*axis* of rotation: if you curl the fingers of your right hand in the
way the rotation goes, your thumb points in the direction of angular
momentum. This definition turns out to be very useful and is used for
other rotational quantities like torque, and it can even account
surprisingly well (and simply) such complex behaviors as the
precession of a gyroscope.

This is a start. Perhaps if you now responded to what you find
interesting in the above or what you are confused about.

PD

G=EMC^2 Glazier · Guest

PD Angular motion creates inertia. This inertia balancing the force of
gravity. This is proving inertia and gravity are two sides to the same
coin. That motion is equivalent to gravity. It fits well with my Spin is
in Theory that I use3 in the quantum micro realm. bert

Saul Levy · Guest

Learn some physics first, Hugh.

Angular momentum is defined best as an equation. Once you understand
that, it>s very easy!

Good luck!

Saul Levy

On Mon, 21 Jul 2008 08:55:12 -0600, Hugh Clary
<badinage@netzero.ZAPTHISnet> wrote:

[quote]I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!

Hugh[/quote]

Michael J. Strickland · Guest

"Hugh Clary" <badinage@netzero.ZAPTHISnet> wrote in message
news:4885a2e8.6123500@news.individual.net...
[quote]I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!

Hugh

[/quote]

Angular momentum is the rotational analog of linear momentum (p = mv).
For a planet moving in an orbit:

L = mvr

That is, it is the [linear momentum of the planet] X [radius of its
orbit].

Also, it is [mass of the object] X [orbital speed ] X [radius of its
orbit].

So Angular momentum increases as mass, orbital speed, and/or orbital
radius increase.

---------------------------------------------------------------------------

For a spinning solid object, the general formula for angular momentum
is:

L = Iw

where:
I = Rotational inertia
w = Angular velocity (e.g. rpm)

Rotational inertia is a measure of how hard it is to spin up the object
(or to stop it once it is spinning). It increases with the mass, and
volume. It also depends on the shape of an object.

--
-----------------------------------------------------------------------
Michael J. Strickland
Quality Services qualityservices2@verizon.net
703-560-7380
-----------------------------------------------------------------------

Timberwoof · Guest

In article <sp0c84hnqf9s5lc6b0qihj034gbm367of6@4ax.com>,
Saul Levy <saullevy1@cox.net> wrote:

[quote]On Mon, 21 Jul 2008 08:55:12 -0600, Hugh Clary
badinage@netzero.ZAPTHISnet> wrote:

I am looking for an understandable definition
of angular momentum. Definitions abound on
the internet, but they are all incomprehensible,
at least to me:

http://tinyurl.com/5tfaxf

Beyond that, apparently the planets Jupiter and
Saturn possess some 90% of our solar system>s
angular momentum, all by themselves.

Can anyone explain these concepts to me, hopefully
in terms that my admittedly poor comprehensive
abilities can follow?

Appreciate it!

Hugh

Learn some physics first, Hugh.
[/quote]
I think it>s fair to assume he>s trying to learn some physics. The
question is a physics question!

[quote]Angular momentum is defined best as an equation. Once you understand
that, it>s very easy!
[/quote]
That>s a nice thought, especially if you>ve developed a day-to-day
familiarity with equations. I>m pretty good at that; I can think through
my way through most things algebraic and slog my way through integrals.
But not everyone is up to even my level, and frankly, it>s not necessary
for a lay understanding of some of the issues involved.

Yes, if someone wants to talk about Goothy things like Sirius emitting
the Moon and sending it here to end up in a nearly circular orbit 12000
years ago, it helps to work out the orbital details with paper and
pencil, much like our silly Brad has never done.

I think that even a basic understanding of what "angular momentum" means
can help someone understand such things as orbits circularizing and
planets locking their rotation to their primary.

Conversely, a good way to make someone resentful is to yell RTFM at him.

--
Timberwoof <me at timberwoof dot com> http://www.timberwoof.com
Official naysayer of the DARPA kind, who knows only of what¹s accepted by
the Old Testament of the Zionist/Nazi New World Order
which refuses to accept or allow deductive reasoning.

Jim Black · Guest

On Tue, 22 Jul 2008 17:31:05 GMT, Michael J. Strickland wrote:

[quote]Angular momentum is the rotational analog of linear momentum (p = mv).
For a planet moving in an orbit:

L = mvr

That is, it is the [linear momentum of the planet] X [radius of its
orbit].

Also, it is [mass of the object] X [orbital speed ] X [radius of its
orbit].

So Angular momentum increases as mass, orbital speed, and/or orbital
radius increase.
[/quote]
That gives you the magnitude of the angular momentum if -- and only if --
the velocity is at right angles to the radius, as in a circular orbit.
Otherwise the formula you wrote needs to be multiplied by sin(theta), where
theta is the angle between v (the veloctity) and r (a vector from the point
it>s orbiting to the planet). Angular momentum also has a direction, which
is perpendicular to both v and r, and consistent with the right-hand rule
(see PD>s post).

For the OP, all of the above is what people mean when they say that angular
momentum for a particle is the mass times the cross product of r and v.

--
Jim E. Black (domain in headers)
How to filter out stupid arguments in 40tude Dialog:
!markread,ignore From "Name" +"<email address>"
[X] Watch/Ignore works on subthreads


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