Buoyancy / energy

[CTho9305]

How much energy does it take to evacuate a 1m^3 volume? Assume this is at some convenient temperature at sea level. If the volume is surrounded by a container that weighs 1kg, how high will it float?

 

[CycloWizard]

How much energy it takes depends on what fluid the volume is filled with and how you try to remove it. Assuming a perfectly efficient removal process, the simplest thing I can think of is that the amount of energy required would be equal to the kinetic and potential energies of the fluid within the control volume (plus, depending on your point of view, the relativistic energy ). If you simply took the contents of the volume and placed them next to it in a gravity-free environment (i.e. no potential energy change), then only the kinetic energy need be considered. How much kinetic energy is present depends on the fluid and conditions. Too tired tonight to work out the details... Maybe tomorrow.

 

[CTho9305]

My guess is 100kJ, and a height of 10km.