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  1. Gh778

    B Energy to increase the radius of a circle composed of several disks

    Hi, I take a big number of disks to composed a circle of a radius of 1 m, the blue curved line is in fact several very small disks: I take a big number of disks to simplify the calculations, and I take the size of the disks very small in comparison of the radius of the circle. The center A1...
  2. Gh778

    B Energy needed to increase a volume

    A recipient (cube) of 1m³ is filled of small spheres, there are for example 1000³ spheres inside the recipient. There are also 1000³ elastics that attract the spheres to the bottom. The elastic are always vertical. One elastic for each sphere. One end of the elastic is fixed on a sphere and the...
  3. Gh778

    Calculate the forces and the work

    Homework Statement A wheel moves to the rigth and rotates like a wheel of a bike. There are 2 bodies: - the wheel (red circle) + 2 red walls - the black arm The ground is fixed. The black arm can rotate around the red axis. The red axis is fixed to the wheel. There is no friction. The...
  4. Gh778

    Calculate a torque from a pressure

    Homework Statement Hi :smile: Calculate the forces F1, F2, F3. F1 is the force on the red wall. F2 is the force on the black center and F3 is the force from springs on the red center. Calculate the torques T1 from F1 and T2 from F2 and give the energy from these torques for and angle of 0.2...
  5. Gh778

    Does this device give a magnetic field?

    Hello, It's a theoretical question. I take 2 electrostatic particules fixed in a circle. I turn the circle. Is there a magnetic field ? I suppose the angular velocity very high and I suppose the particules are fixed in the circle. The diameter of the circle is very small. I don't want the...
  6. Gh778

    The position of a point in 2 rotations with 2 axes

    Homework Statement It's a question I ask to myself. A support turns at ##w_0## and can accelerate. A disk on the support can turn around itself (side view) but at start ##w_1=0##. I done the experimentation with 2 wheels but I'm not sure about my tests. There is an angle between 2 axes: The...
  7. Gh778

    Work of a point on a cycloid

    Homework Statement A wheel turns and moves in translation like a wheel of a bike on the road (cycloid). Inside the wheel there is the pressure P from a gas. Outside the wheel there is no pressure. Calculate the work of a point from pi/2 to pi/2+a. The radius of the wheel is 1. The pressure P...
  8. Gh778

    Sum of torque

    Hi, I imagined this device and I don't understand where is the error. I posted here because it's a simple mechanical device, I have trouble with the sum of torque. The potential energy must be constant. I think I forgot a torque, if you see where ? A torus turns counterclockwise around the...
  9. Gh778

    Delay of propagation of the pressure in a fluid

    Homework Statement Does the delay of propagation of pressure gives a torque during a short time ? A disk full of a liquid turns at a constant angular velocity w around the red axis. At a time, a valve move out, this will increase quickly the pressure inside the liquid. 1/ Draw the lines...
  10. Gh778

    Problem with energy in a cycle

    Hi, I compute sum of energy in a cycle and I don't find 0, could you help me to find the error ? I started an equivalent thread in another physics forum but nobody understand. I hope my english is clear enough for understand the problem. The system is under gravity and everywhere outside...
  11. Gh778

    Pendulum with not homogeneous attraction

    I would like to study a pendulum in 2D, not on Earth but only with one fixed mass attract a disk. Considered this fixed mass like a point. No friction on this theoretical study. The disk can move only around a part of circle. There are only 2 forces, F the attraction and N the force from wall...
  12. Gh778

    Liquid helium and curved piston

    It's a theoretical study. Like the image showing, the curved piston move in container and need energy for that. In the same time, another piston move up and recover energy. The pressure inside container is always the same (need to control speed of pistons, but there is a pressure). No gravity...
  13. Gh778

    Pressure on a curved surface

    For compute force from pressure on a surface, do I need take in account the red force ? When an atom press a surface it press atoms at right and at left, this increase the pressure on the curved surface if the volume is closed ? http://imageshack.us/a/img823/3852/66o4.jpg [Broken] Or...
  14. Gh778

    How to calculate sum of torque ?

    I would like to calculate sum of torque on object composed of one container of helium II liquid and one container of gas with low pressure. I know you think it's 0, but I would like to be sure (I think it's not 0, but it's only my intuition). It's not a theoretical problem, so I take in account...
  15. Gh778

    Density in water

    I would like to know if density is exactly the same everywhere in a disk full of water except at one part where there is gas. All are fixed: disk of water, and container of gas. I don't want the value of density just to know if density is exactly the same everywhere in disk of water. 2 cases...
  16. Gh778

    Pressure and gravity forces

    I would like study a theoretical problem. A system composed of 2 spheres can move at left of at right in water. One sphere has gas at low pressure and other sphere has water in it. The wall of spheres are very thin and has the same density of water. Sphere of gas don't has force because it has...
  17. Gh778

    Choose parameters for a system

    Theoretical study. Disks are one above the other. Turn at same rotationnal speed w. 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...
  18. Gh778

    Pressure inside a liquid planet in rotation

    Hi, I would like to calculate the pressure inside a liquid planet in rotation. How can I do ? Pressure depend of depth under gravity but it depend of rotational speed too. Is it gravity pressure less centripetal pressure ? Is it \frac{1}{2}ρω^2r^2 - ρgh ?
  19. Gh778

    Temperature around a bubble of air in water

    1/ Like density in water change with depth, the number of chocs (from temperature) is not the same all around the bubble. The bubble have an additional up force I think. But the weight is directly the volume of bubble by the density of water. The weight can be change with temperature ? Maybe...
  20. Gh778

    Why weight change when I put effervescence tablet ?

    Hi, I measure weight of : column of water + water + effervescence tablet + cover (hermetic) When I put effervescence tablet (give a lot of small bubbles) in water and close very quickly the cover, the weight decrease of 0.2g with a precision of 0.01g for the weight-balance. The weight...
  21. Gh778

    Bubble in a water column

    On Earth. Theoretical study. With a perfect liquid (no viscosity). A bubble in a column of liquid is moving up, the column is on a table, I have some questions: 1/ the force on the table increase/decrease when bubble is moving up ? 2/ the center of gravity of {column+liquid} is always the same...
  22. Gh778

    Sum of forces, vacuum and gravity

    It's a theoretical study. I would like to understand how the sum of forces can be at 0 if I put an object (vacuum in it) in a big liquid disk (disk is fulled with liquid), the disk is big enough for agglomerate liquid (like this works with a planet, matter is agglomarate with gravity). There is...
  23. Gh778

    How is pressure on an object ?

    I would like to know how is the pressure on an object (black on figure). The pressure is not a classical pressure like gas but is given by macroscopic balls. Balls are like magnets, North pole outside and South pole inside with iron for give roads to magnetic fields (see figure). All balls...
  24. Gh778

    Sum of forces

    I'm drawing a cone (black color) inside balls. Balls are pressured from external force, but the pressure is fixed. Balls repuls themselves and cone repuls balls too. The cut view of cone (bot) showing part of balls all around cone, arrows are forces all around balls. For me F1>F2, because like...
  25. Gh778

    Balloon on Earth

    Imagine a balloon with nothing in it except two masses M1 and M2, like first drawing. The gas of atmosphere apply a force to move up Fgas, and the weight apply a force to move down Fm1+2. Weight of M1+M2 is equal to the force from gas (opposite direction). Now, rotate M1 and M2, like that the...
  26. Gh778

    Efficiency to move a curve shape

    Fig 1 : the blue volume has a lot of very small spherical balls in it. Balls are under pressure from external system (weight or other), the potential energy is always the same because the blue volume is constant. When I move the blue volume from position 1 to position 2, I can understand that...
  27. Gh778

    Torque in a curve shape

    Hi, I'm interesting about the torque in the system like I drawn. I drawn only additional forces from curve, not the true forces from absolute pressure. The shape is full with a lot of very small circular balls (blue color). A pressure is apply from external system. The goal is to have FR...
  28. Gh778

    Pressure forces from a liquid in rotation

    Hi, A liquid in rotation give two kind of forces: 1/ centripetal 2/ pressure forces (Fa, Fb in the drawing) I'm ok that centripetal forces can't give energy (we lost kinetics energy) but Fa/Fb seems in direction to external circle, why it's not possible to recover energy from these...
  29. Gh778

    Recover energy from unique temperature

    Why is not possible to use this simple cycle for recover energy from unique temperature ? 1/ (first drawing) For limited friction I think it's possible to put outside pressure of 10 nPa. The speed velocity of the cylinder is constant, I think it's possible to use small speed like 20 m/s but...
  30. Gh778

    Centrifugal forces + pressure and CG

    Take half torus with solid part of density 1, other half torus with liquid of density 1. The torus turn at W rd/s enough for maintain liquid at external circle. Now, for 0 to 180° we accelerate torus, this increase forces (blue in drawing) from pressure of water and from 180° to 360° we...
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