Is buoyancy possible without gravity?

[scientifico]

Hello, does bouyancy exist if there isn't the force of gravity but i push down the object in the water with my force?

thanks!

 

[Doc Al]

The buoyant force on an object is due to the pressure of the fluid on the object. But without gravity there would be no pressure and thus no buoyant force.

Does that address your question?

 

[pallidin]

The buoyant force on an object is due to the pressure of the fluid on the object. But without gravity there would be no pressure and thus no buoyant force.

Does that address your question?

I thought that, say, a gallon of water(in the form of a sphere, for example)in deep space does not spontaneously separate into H2O molecules; rather that the "sphere" is maintained.

As such, a bubble within that water sphere would experience pressure; forcing the bubble to the exterior.

Could be totally wrong though...

 

[Andy Resnick]

Hello, does bouyancy exist if there isn't the force of gravity but i push down the object in the water with my force?

thanks!

The origin of "bouyancy" is from differences in density; gravity is usually the relevant force but any force will do, for example the centripetal force.

So, buoyant flow can occur in the absence of gravity; for example, you can separate air from water in space by rotating the container- the air will migrate to the center.

 

[Doc Al]

The origin of "bouyancy" is from differences in density; gravity is usually the relevant force but any force will do, for example the centripetal force.

Good point! (Although I'd say differences in pressure give rise to buoyancy, but a rotating system can certainly create a pressure gradient.)

 

[Doc Al]

I thought that, say, a gallon of water(in the form of a sphere, for example)in deep space does not spontaneously separate into H2O molecules; rather that the "sphere" is maintained.

As such, a bubble within that water sphere would experience pressure; forcing the bubble to the exterior.

Could be totally wrong though...

Sure, there'd be some small force.

 

[fxm99]

As such, a bubble within that water sphere would experience pressure; forcing the bubble to the exterior.

That does not exactly appear to be happening here:

Waves, Bubbles and Reactions in a Free Sphere of Water


Ep.14 Antacid tablet reacting in a water sphere in space

 

[maburne2]

This is a great point, there should always be a buoyancy effect; on earth, buoyancy is a consequence of Archimedes principle, it is clearly observable due to Earth's great mass and therefore formidable local gravitation field. However, a globular formation of water in space will still have a buoyancy effect provided by reaction due to the localized gravitational pull between each water molecule and also the energy in hydrogen bonds.

 

[Creator]

..., you can separate air from water in space by rotating the container- the air will migrate to the center.

Good point;
Can also do it on earth... called a centrifuge...high g's separate more quickly ...even radioisotopes ...(luckily, Iran has yet to figure out how to perfect it. ;)) ..Or was it stuxnet that tripped them up?) ;)) he, he.


...

 

[Andy Resnick]

Good point! (Although I'd say differences in pressure give rise to buoyancy, but a rotating system can certainly create a pressure gradient.)

I agree- since density is a continuum concept, pressure (or stress) is more appropriate than 'force'.

 

[HallsofIvy]

I thought that, say, a gallon of water(in the form of a sphere, for example)in deep space does not spontaneously separate into H2O molecules; rather that the "sphere" is maintained.

As such, a bubble within that water sphere would experience pressure; forcing the bubble to the exterior.

Could be totally wrong though...

Of course, the reason the sphere does not separate and bubbles "rise" to the exterior, is because of the gravitational force between molecules of water so this doesn't really fit your "no gravity" requirement.

 

[pallidin]

Of course, the reason the sphere does not separate and bubbles "rise" to the exterior, is because of the gravitational force between molecules of water so this doesn't really fit your "no gravity" requirement.

I think the OP is positioning his question with regards to external gravitational influence.
OP(Scientifico): Can you clarify?

 

[SpectraCat]

Of course, the reason the sphere does not separate and bubbles "rise" to the exterior, is because of the gravitational force between molecules of water so this doesn't really fit your "no gravity" requirement.

Umm ... perhaps not ... the intermolecular forces, such as hydrogen bonding, between the water molecules are many many orders of magnitude greater than the gravitational force. I suppose that in the case of a planet-sized sphere of water, gravitation might be a significant factor, but I don't really think that was what was being discussed in this example.