Misplaced Pages

Revision as of 12:49, 7 April 2006

This page unintentionally left non-blank.

Coriolis effect (2)

I noticed you added a request for cleanup to the coriolis effect article. I think just about all of the crititism on the Coriolis Talk page is written by me. My intention is to address the issues surrounding the coriolis effect, but to do that I need to complete some more diagrams and animations.

My approach is to use analogies between rotating disks and the rotating Earth. --Cleonis | Talk 16:19, 16 February 2006 (UTC)

Please don't. The Coriolis effect is not limited to the Earth, and the sphericity of the earth just confuses matters. When explaining Coriolis, limit discussion to rotating discs and everything will be much, much clearer. After that, discuss what this means on the Earth. And remember, if it make any difference whether motions are North/South or East/West your example is *not* demonstrating the Coriolis effect. -- GWO

What you describe is what I have in mind: first discussion of purely 2-dimensional cases, and only then move on to showing how those insights can be applied to wind patterns and ocean currents.

In (the thumbnails of) the diagrams on the right a rotating disk is represented, with on it a box. The box is co-rotating with the disk. The box represents an accelerometer; when the box is accelerating then the weight suspended on springs inside moves to one side of the box.

Well, that looks like a great explanation of centripetal force, but centripetal force is not Coriolis. Fixing the box to the disc is flat out wrong: Unless the box is moving relative to the disc, there's no Coriolis.

That illustrates the usefullness of animations. The arrows in the diagram represent motion with respect to the disk, but making an animation is clearer. In this example, the box has all the time the same angular velocity as the disk, but when it moves closer to the center of rotation then the accelererometer registeres an acceleration perpendicular to the motion towards the center of rotation. You have shown to me it is worthwile to make that animation. --Cleonis | Talk 11:53, 17 February 2006 (UTC)

You have confused me again, or you have confused Coriolis and Centrifugal... The Coriolis force doesn't care whether you move closer to the center of rotation. The location of center of rotation does not appear in the Coriolis terms. If you have to make reference to the location of the center, as opposed to the direction of the rotation, you are not dealing with Coriolis but centripetal force.

Incidentally, on the subject of relative motion, I'm confused by the discussion of the parabolic surface on the rotating table. Surely, after spin-up, the fluid is in solid-body rotation (i.e. stationary relative to the dish). Is this right?

several hundreds of articles link to the coriolis effect article, and I estimate that half of those deal with meteorological phenomena and oceanographic phenomena. Many textbooks state that 'the coriolis effect' is in fact involved in wind patterns and ocean current patterns, so the coriolis effect article must deal with that issue. --Cleonis | Talk 19:14, 16 February 2006 (UTC)

That's why I said After that, discuss what this means on the Earth. But if you set your initial examples, on the earth, other effects mask what is really Coriolis.

Rotating parabolic dish

I copy and paste from above:

the discussion of the parabolic surface on the rotating table. Surely, after spin-up, the fluid is in solid-body rotation (i.e. stationary relative to the dish). Is this right?

I introduced the rotating parabolic dish in the coriolis effect article because I think the educational demonstrations of the MIT fluid dynamics lab are very helpful.

Of course, when a body of fluid has is in continuous solid body rotation then no part of the fluid is moving relative to the dish, hence no coriolis effects. (I have written about spinning up to solid body rotation and spinning down again in the mercury mirror article.)

It gets interesting again when there are disturbances in that rotating body of fluid. For example, the phenomenon of inertial oscillation in oceans as described in oceanography. My next plan is to make an animation that depicts schematically this inertial oscillation being modeled with a layer of fluid on a rotating parabolic dish.

The actual dish can be very flat: the parabolic disc used for this MIT lab demonstration is about a meter in diameter, and the center is about a centimeter lower than the outer rim. --Cleonis | Talk 18:04, 19 February 2006 (UTC)

roadway air dispersion

thanks for your comment on the equation. you were on target in your point. i have made the necessary fix, which actually was to change the definition of the variable "c", which is a dimensionless variable measured in radians, best regards Covalent 20:28, 17 March 2006 (UTC)

RfAr Monicasdude

As one of the advocates of the first RfC, you may be interested in having a look at this. - Best regards, Mailer Diablo 21:53, 6 April 2006 (UTC)

Rugby union positions

I want to retain the sentence about the laws specifying certain positions in the scrum but I want to include your knowledge of law 20 (obviously better than mine). Your edit summary said that 3-5-1 was permissable by the laws, did you mean 3-4-1?GordyB 12:18, 7 April 2006 (UTC)

Yes, sorry I meant 3-4-1. Law 20 says

"The two players in the second row who push on the props and the hooker are the locks. The outside players who bind onto the second or third row are the flankers." (emphasis mine)

Clearly, binding on the second row is allowed, and that's 3-4-1.