[LB7 (OP)]

The device:


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With:


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The sum of the energy with the pressure like that:


f12.png (43.57 kB . 921x491 - viewed 2241 times)

With dV the difference of the volume of the spheres (smaller/bigger), v is the volume of a smaller sphere

I recover an energy dV*2p1 because I reduce the size of the spheres where the pressure is 2p1
I need an energy 2p1*v to move in the new smaller sphere
I move to the right the orange sphere, I recover the energy from the translation of the spring I noted W
I recover an energy because I move out the orange sphere in the blue area v*p1
I need an energy dV*p1 to increase the size of the sphere

Sum of energy W +v*p1 or W is the energy I recover from the move out/in (if I do that).