Choose parameters for a system

In summary, the conversation discusses the theoretical study of disks that are stacked on top of each other and rotate at the same speed. The main question is whether it is possible to choose good parameters for density, radius, rotational speed, position of d3/gas, and size of the disk in order to produce certain forces on the system. The answer is no, as there are no easy choices of parameters that will result in the desired forces. The conversation also touches on the concept of centrifugal gravity and the idea of perpetual motion. Ultimately, the conclusion is that it is important to consider all forces involved when studying this system.
  • #1
Theoretical study. Disks are one above the other. Turn at same rotationnal speed [itex]w[/itex].

Is it possible to choose good parameters for:

- density
- radius
- rotationnal speed
- position of d3/gas: d3 in disk1 at radius R1, d3 in disk2 at radius R2, gas in disk1 at radius R2, gas in disk2 at radius R1
- size of disk

For have forces like I drawn on the system ?

NB: disk must be big enouh for have gravity effect (1000 km for example). Center of rotation is supposed fixed.


  • d1.png
    15.5 KB · Views: 406
Last edited:
Physics news on
  • #2
No - there are no easy choices of parameter that will produce the results you have drawn.
BTW: the green one is nonsense.

Looking at the blue one:
I can see what you are doing - you think the buoyancy and weight will add to a net tangential force.
Centrifugal gravity does not work like you seem to be thinking.

You realize this is perpetual motion?
Therefore it does not work...

Some notes:
It does not matter how big the disks are - all you need is enough rotation to get the pressure of the liquid to vary with the radius so it is highest at the rim... and you want the blue liquid to be light enough to have zero drag effect.

Make sure you have included all the forces.
  • Like
Likes 1 person
  • #3
Since the time I posted the thread I understood. thanks for your help.

1. What are parameters in a system?

Parameters in a system refer to the measurable quantities or variables that affect the behavior or output of the system. They can include physical characteristics, environmental factors, and user inputs.

2. How do you choose parameters for a system?

Choosing parameters for a system involves identifying the key variables that will impact the functioning of the system and determining their acceptable range or values. This can be done through research, experimentation, and analysis of the system's requirements and objectives.

3. What factors should be considered when selecting parameters for a system?

When selecting parameters for a system, factors such as the system's purpose, functionality, limitations, and potential risks should be considered. It is also important to consider the accuracy and reliability of the data used to determine the parameters.

4. How do you ensure the chosen parameters are suitable for the system?

To ensure the chosen parameters are suitable for the system, it is important to test and validate them through simulations or prototypes. This can help identify any potential issues or limitations and make necessary adjustments.

5. Can parameters be changed after the system has been implemented?

Yes, parameters can be changed after the system has been implemented. However, this should be done carefully and with thorough testing to ensure that the changes do not negatively impact the system's functionality or performance.

Suggested for: Choose parameters for a system