A rotating frame equation for the "carousel experiment"

[Simon F]

TL;DR

The "carousel experiment" is the worst case to show the Coriolis force despite claims it show the "Coriolis effect".

As was repeatedly shown by Anders Persson,

https://rmets.onlinelibrary.wiley.com/doi/10.1002/qj.2477
<link removed>

the "carousel experiment" is a poor case to show the Coriolis force despite claims it show the "Coriolis effect". Indeed, the Coriolis force, if it was alone (which is true for an elastoid), would should a narrow circle that oceanographers know well under the misleading term "inertia circle", quite different from the wide deflection occuring in the "carousel experiment".

This led me to a very short exercise:

An alternative rotating frame equation, without the Coriolis force, is simply as follows:
a_r = a_a - 2 Ω x v_a + a_cp
with a_cp a centripetal term

In the "carousel experiment", a_a=0 and v_a=cst => a_r = cst + a_cp .

The Coriolis equation was implicitly a choice made by G.Coriolis because he has chosen not to try another decomposition whereas geometry allows an infinite choice and in some cases there are better choices than his. Geophysicists understood afterwards that his decomposition is exactly the right one to show the fundamental "elastoid-inertial" planetary mode, but this is another story, very different from the "carousel experiment" (which does not include any elastoid).

 

[Dale]

What is the carousel experiment?

 

[Roberto Pavani]

Foucault is the answer / corollary

 

[Simon F]

The carousel

What is the carousel experiment?

In the context of the Coriolis force, the carousel experiment is the observation of an all straight motion by one sitting on a rotating carousel.
For a disputable reason, this carousel experiment has been tied to the "demonstration of Coriolis force" which explains its huge success. I have worked in the same idea of a Newton-like equation, as G.Coriolis did, but with other terms which are maybe more intuitive to this carousel experiment.

 

[Dale]

In the context of the Coriolis force, the carousel experiment is the observation of an all straight motion by one sitting on a rotating carousel.

So you start with an inertially moving object and you simply write its equation of motion in the rotating frame?

Is it supposed to be just one inertial motion or is the process repeated with multiple inertial motions? Your description is very unclear.

For a disputable reason, this carousel experiment has been tied to the "demonstration of Coriolis force" which explains its huge success.

That something is “disputable” is uninformative. Some people will dispute anything, even whether the earth is round. Here the standard is whether something is disputed in the modern professional scientific literature.

I have not seen any professional scientific literature disputing the Coriolis force based on what you call the carousel experiment. Even the reference you give in the OP doesn’t do that as it is discussing non-inertial motion.

Do you have any actual professional scientific reference that makes this claim?

 

[Simon F]

Hello,
You can read Persson 2015 in details which is the most documented article recently.
Also you can read Edwards and Edwards 2021.

The carousel experiment is famous for the Coriolis force topic, I am not lying. Irony is that it is a poor/fake demo of the force. The Coriolis force is a mode that can enter any modal decomposition of a signal depending on the modellist choice. It is meaningless saying that you can demonstrate...a modellist choice!

 

[Dale]

You can read Persson 2015 in details which is the most documented article recently.

The one you linked to above? It doesn't even support your claim.

Also you can read Edwards and Edwards 2021.

Give the actual reference.

The carousel experiment is famous for the Coriolis force topic, I am not lying. Irony is that it is a poor/fake demo of the force. The Coriolis force is a mode that can enter any modal decomposition of a signal depending on the modellist choice. It is meaningless saying that you can demonstrate...a modellist choice!

If something is a matter of choice then it can be chosen. If it is a matter of choice then the most that can possibly be shown is that other choices are possible, which is already implied in the fact that it is a matter of choice.

Do you think that scientists are unaware of the fact that the Coriolis force is a matter of choice?

 

[Simon F]

Hello,

Persson 2015 :

"whereas the condition that the Coriolis force is solely responsible for the deflection is justified on a rotating planet, but not on a turntable" [turntable=small carousel].

"A proper intuitive understanding of the [Coriolis-only] deflection over a rotating planet, on a rotating parabola or in a rotating water tank, might require more mental effort than a scant reference to the ‘illusory’ [not Coriolis-only] deflection over a turntable"

This is my topic introduction: the carousel experiment is a poor case to demonstrate the Coriolis force since the deflection is not Coriolis-only.