Weight of a cone in a fluid

[m441]

I replace fluid by a lot of perfect compressible balls (theoric case). I put a solid cone in a recipient. Around the cone balls place themselves like circles. For me circles prevent to put all pressure. But like this all balls around the cone want to move up, so the weight of the cone is greater than real weight and I don't find the solution.

[m441]

I drawn details of forces, like I think they are. Magenta force are give from aside balls. It's not a perfect scale just for watch details. Maybe you can find where I'm wrong ? Ok, if cone move the shape of balls can't be a perfect circle, but a part of pressure is removed on cone. I imagine the recipient like cylinder for keep the shape.

[m441]

I don't know why, but the last image in my previous message is break... see below:

http://**invalid link**/photo/my-images/189/i487.png/



I would like to add: with an 2D object, I can understand all forces at red zone (image) compensate themselves:



But with 3D object, a part of cone (slope) is surrounded by circles formed by balls, the plane base has nothing in particulary.

Do you know where is the compensation ?

[m441]

I think I have the answer: for each circle, like radius increase, force increase if nothing compensate it, this would give more force to small radius but aside balls are there for compensated this force. Do you watch the solution like that ?

[m441]

I thought another system when balls can give a torque, if I imagine a thread like drawing with "perfect" magnetic balls, the difference of radius can't compensated themselves:

[m441]

I found a 3d object easier to study: a spiral composed with a cylinder and a cone. Without cone I'm ok with torque is 0 but with cone, balls have F force that reduce force in this part of spiral, so where is the another force for have torque to 0 ?

[m441]

Maybe it's easier to see there is a problem with pressure under system with gravity. Red forces are different than black forces and due to the gravity the top of the shape can't compensate. Balls repuls themselves like 1/d².

[m441]

this link:

http://www.colorado.edu/physics/phys332 ... Needle.pdf

speak about density charge and like I suppose it's not the same density everywhere, so I don't know how torque could be at 0