| Author |
Message
|
| phirong |
 Posted: Thu May 01, 2008 6:35 pm Post subject: Principal Axes of Inertia (a challenge) |
 |
|
Forum Freshman
Joined: 01 May 2008
Posts: 1
|
Hi scientists.
I am a programmer and I've been asked to get the (Principal Axes of Inertia) given only the coordinates.
I've been searching for a formula for the Principal Axes of Inertia with a given values of (x,y) axes.
Example:
0,4
12,59
10,100
3,498
But I can't find anything related to my problem.
Is it possible to get Principal Axes of Inertia given only the coordinates?
Sorry, I don't have any idea. I'm asking for your help.
I'm not even sure if I posted on the right section.
Thanks in advance.
-
phirong |
|
| Back to top |
|
 |
| William McCormick |
| Posted: Fri May 02, 2008 4:48 pm Post subject: Re: Principal Axes of Inertia (a challenge) |
|
|
Forum Ph.D.
Joined: 03 Apr 2008
Posts: 828
|
| phirong wrote: |
Hi scientists.
I am a programmer and I've been asked to get the (Principal Axes of Inertia) given only the coordinates.
I've been searching for a formula for the Principal Axes of Inertia with a given values of (x,y) axes.
Example:
0,4
12,59
10,100
3,498
But I can't find anything related to my problem.
Is it possible to get Principal Axes of Inertia given only the coordinates?
Sorry, I don't have any idea. I'm asking for your help.
I'm not even sure if I posted on the right section.
Thanks in advance.
-
phirong |
I have seen just about every crazy device on earth. But I have never heard that term before.
The word inertia actually did not mean movement. It might have been misunderstood, in its use by the Universal Scientists. And then later changed to fit some other scheme.
In other words if something is just sitting there, it is really not just sitting there. It is on a spinning planet, revolving around a sun. And only God knows what our solar system is doing. And or the Universe.
Click on the image to view it at its original size
Today in physics it means either rest or straight line motion.
Axes means Axis. And can be the pin in a door hinge, or the imaginary line from the North to South Poles. That the planet revolves around.
From those two dimensional coordinates, I would have trouble deciphering what they want.
You could assume that the origin of the two coordinates given is zero. That could be the axis and the other two coordinates might give you the objects radius. From that you could assume some gravitational force. And then decide what you want because I have no clue. Ha-ha.
Sincerely,
William McCormick
_________________
http://www.Rockwelder.com |
|
| Back to top |
|
|
| serpicojr |
| Posted: Fri May 02, 2008 5:37 pm Post subject: |
|
|
Forum Professor
Joined: 17 Jul 2007
Posts: 1128
Location: JRZ
|
phirong: Ignore William McC.
I'm sure someone here should know enough classical mechanics to help you out. I don't. However, if nobody steps up, I might be able to help if you explain what the given coordinates are supposed to represent.
William: This isn't some sort of new-fangled concept. Euler was talking about it in 1730. We knew you didn't know anything about modern physics, but now it's clear you just don't know anything about physics period. |
|
| Back to top |
|
|
| William McCormick |
| Posted: Fri May 02, 2008 5:45 pm Post subject: |
|
|
Forum Ph.D.
Joined: 03 Apr 2008
Posts: 828
|
| serpicojr wrote: |
phirong: Ignore William McC.
I'm sure someone here should know enough classical mechanics to help you out. I don't. However, if nobody steps up, I might be able to help if you explain what the given coordinates are supposed to represent.
William: This isn't some sort of new-fangled concept. Euler was talking about it in 1730. We knew you didn't know anything about modern physics, but now it's clear you just don't know anything about physics period. |
I do understand any force in the Universe. I openly admit I do not use modern terms, and I am proud of that. History shows that most of the older terms have changed many times over the last 100 years.
I only get in trouble when I try to communicate with modern terms. Because the terms are so useless by definition.
Sincerely,
William McCormick
_________________
http://www.Rockwelder.com |
|
| Back to top |
|
|
| serpicojr |
| Posted: Fri May 02, 2008 6:24 pm Post subject: |
|
|
Forum Professor
Joined: 17 Jul 2007
Posts: 1128
Location: JRZ
|
| A rose by any other name would smell as sweet. Take a minute, spend a little effort, try to learn what terms mean in terms of what you're used to. Dismissing something simply because it's couched in language with which you're not familiar is silly. It's all just... words, words, words! |
|
| Back to top |
|
|
| William McCormick |
| Posted: Fri May 02, 2008 6:53 pm Post subject: |
|
|
Forum Ph.D.
Joined: 03 Apr 2008
Posts: 828
|
| serpicojr wrote: |
| A rose by any other name would smell as sweet. Take a minute, spend a little effort, try to learn what terms mean in terms of what you're used to. Dismissing something simply because it's couched in language with which you're not familiar is silly. It's all just... words, words, words! |
Almost any term that has stuck today. Whether it be new or old. Is the worst term possible. The terms of today are almost all backwards. Because the basic terms are backwards or misapplied.
I check the terms out, and then try to decipher what simple thing they are complicating. I have no other reason to figure them out. I can do anything I wish, I have no scientific limitations. I am just a little short of manpower.
Sincerely,
William McCormick
_________________
http://www.Rockwelder.com |
|
| Back to top |
|
|
| KALSTER |
| Posted: Fri May 02, 2008 7:22 pm Post subject: |
|
|
Forum Professor
Joined: 08 Sep 2007
Posts: 1905
Location: South Africa
|
For how long will this lunatic have free reign? William, you reach new levels of delusion on a dayly basis. I don't have any pull to get you banned, but I can assure you that if I had been a moderator, I would certainly have requested such from the admins. You are severely damaging the credibility of this forum with your unchecked and frequent presenting of your personally derived "theories" as fact, despite many appeals for you to restrain yourself.
_________________
"Gullibility kills" - Carl Sagan |
|
| Back to top |
|
|
| William McCormick |
| Posted: Fri May 02, 2008 7:44 pm Post subject: |
|
|
Forum Ph.D.
Joined: 03 Apr 2008
Posts: 828
|
| KALSTER wrote: |
| For how long will this lunatic have free reign? William, you reach new levels of delusion on a dayly basis. I don't have any pull to get you banned, but I can assure you that if I had been a moderator, I would certainly have requested such from the admins. You are severely damaging the credibility of this forum with your unchecked and frequent presenting of your personally derived "theories" as fact, despite many appeals for you to restrain yourself. |
Well, what is the simple solution to the problem posted?
What technical information that I posted did you disagree with?
Sincerely,
William McCormick
_________________
http://www.Rockwelder.com |
|
| Back to top |
|
|
| (Q) |
| Posted: Fri May 02, 2008 8:19 pm Post subject: |
|
|
Forum Professor
Joined: 12 May 2005
Posts: 1179
|
| KALSTER wrote: |
| For how long will this lunatic have free reign? William, you reach new levels of delusion on a dayly basis. I don't have any pull to get you banned, but I can assure you that if I had been a moderator, I would certainly have requested such from the admins. You are severely damaging the credibility of this forum with your unchecked and frequent presenting of your personally derived "theories" as fact, despite many appeals for you to restrain yourself. |
I see no problem in Bill's daily delusional fixations. He is equally ignored by all as a relatively harmless imbecile, which unto itself provides great value and credibility to this forum by keeping him around to bleat that which is unfathomable gibberish.
He could be our pet monkey.
_________________
I may have no understanding of the current theory of evolution. But that's because science keeps changing it. A few weeks ago I read in the newspaper that it had once again been adjusted & just the other day I discovered a new book called "The New Theory of Evolution" ~~Steven Titchenell : W.V.B.I.G. President. |
|
| Back to top |
|
|
| William McCormick |
| Posted: Fri May 02, 2008 8:48 pm Post subject: |
|
|
Forum Ph.D.
Joined: 03 Apr 2008
Posts: 828
|
| (Q) wrote: |
| KALSTER wrote: |
| For how long will this lunatic have free reign? William, you reach new levels of delusion on a dayly basis. I don't have any pull to get you banned, but I can assure you that if I had been a moderator, I would certainly have requested such from the admins. You are severely damaging the credibility of this forum with your unchecked and frequent presenting of your personally derived "theories" as fact, despite many appeals for you to restrain yourself. |
I see no problem in Bill's daily delusional fixations. He is equally ignored by all as a relatively harmless imbecile, which unto itself provides great value and credibility to this forum by keeping him around to bleat that which is unfathomable gibberish.
He could be our pet monkey. |
You couldn't afford the bananas.
I have found axes inertia, it was on Ebay.
http://www.Rockwelder.com/EastWood/spinningthing.wmv
Sincerely,
William McCormick
_________________
http://www.Rockwelder.com |
|
| Back to top |
|
|
| William McCormick |
| Posted: Fri May 02, 2008 9:26 pm Post subject: |
|
|
Forum Ph.D.
Joined: 03 Apr 2008
Posts: 828
|
| (Q) wrote: |
| KALSTER wrote: |
| For how long will this lunatic have free reign? William, you reach new levels of delusion on a dayly basis. I don't have any pull to get you banned, but I can assure you that if I had been a moderator, I would certainly have requested such from the admins. You are severely damaging the credibility of this forum with your unchecked and frequent presenting of your personally derived "theories" as fact, despite many appeals for you to restrain yourself. |
I see no problem in Bill's daily delusional fixations. He is equally ignored by all as a relatively harmless imbecile, which unto itself provides great value and credibility to this forum by keeping him around to bleat that which is unfathomable gibberish.
He could be our pet monkey. |
In all seriousness did you read the Wikepedia inertia definition. That is really out there.
http://en.wikipedia.org/wiki/Moment_of_inertia
That is sad. They missed the whole point of what takes place with a moving object. An object only likes to travel in a straight line.
If you increased the gravity on a satellite, that was in a stable orbit above a point on the surface of the earth, it would start to fall in towards the planet. And it would orbit the earth faster.
When an ice skater pulls her arms in. She expends energy, by pulling her arms in. She creates the effect of her arms being put under more gravity, like a satellite would react to more gravity.
Sincerely,
William McCormick
_________________
http://www.Rockwelder.com |
|
| Back to top |
|
|
| Dishmaster |
| Posted: Sat May 03, 2008 2:29 am Post subject: |
|
|
Forum Junior
Joined: 30 Apr 2008
Posts: 258
Location: Heidelberg, Germany
|
| William McCormick wrote: |
http://en.wikipedia.org/wiki/Moment_of_inertia
That is sad. They missed the whole point of what takes place with a moving object. An object only likes to travel in a straight line.
If you increased the gravity on a satellite, that was in a stable orbit above a point on the surface of the earth, it would start to fall in towards the planet. And it would orbit the earth faster.
When an ice skater pulls her arms in. She expends energy, by pulling her arms in. She creates the effect of her arms being put under more gravity, like a satellite would react to more gravity. |
And what do you think is wrong there? This is all about a rigid body and how it spins. The example of this ice skater is also correct, but it is no contradiction to what is explained there. Did you notice that the inertia of a rigid body (against change of rotational states) is dependent on the mass distribution (sum over m times r)? The angular momentum L=I*omega is conserved in this example (as it should), because the mass of the skater is redistributed. So, I (inertia) changes, and as a consequence omega (angular velocity) has to change as well.
If I remember well (classical mechanics lectures have been a long time ago), the Principle Axes of Inertia are something like a coordinate transformation of the inertia tensor of a rigid body to three main axes. In an experiment, you would notice these axes as the main rotation axes. It is all very easy for simple bodies (cylinders or spheres) but can be very complicated for arbitrary bodies. As you can break down any translatory movement in the three base coordinates of the 3D space, you can describe every rotation as a superposition of rotations around the principle axes. But I have forgotten how to actuelly calculate them. But WMcC's link should give you at least a hint. There are also other links that could help. |
|
| Back to top |
|
|
| JaneBennet |
| Posted: Sat May 03, 2008 2:53 am Post subject: |
|
|
Forum Masters Degree
Joined: 06 Apr 2008
Posts: 594
|
| phirong wrote: |
I am a programmer and I've been asked to get the (Principal Axes of Inertia) given only the coordinates.
I've been searching for a formula for the Principal Axes of Inertia with a given values of (x,y) axes.
Example:
0,4
12,59
10,100
3,498
But I can't find anything related to my problem.
Is it possible to get Principal Axes of Inertia given only the coordinates? |
Hi Phrong.
For a two-dimensional object I would guess that the main rotation axis (taking Dishmaster’s word for it that this is the same as the principal axis of rotation  ) would be the axis perpendicular to the object and passing through the centre of mass.
If the area bounded by the given co-ordinates has uniform density, then the centre of mass coincides with the centroid, which is given by a simple formula: the centroid of the area bounded by the n points (x1,y1), (x2,y2), …, (xn,yn) is  , where
By the way, Phrong, there’s another useful thing you can do around here. Click the following link: http://www.thescienceforum.com/ignore.php?mode=add&username=William%20McCormick
_________________
“A problem worthy of attack
Proves its worth by fighting back.”
– Piet Hein
Did You Know?
Fact of the day: Ferdinand von Lindemann |
|
| Back to top |
|
|
| Dishmaster |
| Posted: Sat May 03, 2008 3:05 am Post subject: |
|
|
Forum Junior
Joined: 30 Apr 2008
Posts: 258
Location: Heidelberg, Germany
|
Ah, very useful. Cheers! |
|
| Back to top |
|
|
| (Q) |
| Posted: Sat May 03, 2008 7:19 am Post subject: |
|
|
Forum Professor
Joined: 12 May 2005
Posts: 1179
|
This appy should help visualize tensor change in inertia for more complicated mass configurations.
http://demonstrations.wolfram.com/PrincipalAxesOfInertia/
_________________
I may have no understanding of the current theory of evolution. But that's because science keeps changing it. A few weeks ago I read in the newspaper that it had once again been adjusted & just the other day I discovered a new book called "The New Theory of Evolution" ~~Steven Titchenell : W.V.B.I.G. President. |
|
| Back to top |
|
|
|
|
