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Author Topic: am i missing something obvious?  (Read 8347 times)

shipto

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am i missing something obvious?
« on: October 02, 2009, 11:29:32 PM »
My idea is a firm but flexible tube extruded to have air pockets. take a tank of water with a lip seal at the bottom to suit the tube. feed the tube into the tank pass it over pulleys to form a loop then fill the tank. the air pockets would float up hopefully with enough power to pull the tube through the lip seal.

To partly answer my own question I suppose that the pressure to seal the water around the tube may exceed the the force gained from those air pockets floating to the top?

onthecuttingedge2005

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Re: am i missing something obvious?
« Reply #1 on: October 03, 2009, 01:10:06 AM »
I assume you would being using a seal for the bottom of the container. this seal will cause vacuum issues and friction(drag) issues.

the weight of the boxes outside the container will out weight the bouyancy of the boxes in the container which is another issue.

just with these three issues it will not work. there are more issues when your done with those.


Comassion

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Re: am i missing something obvious?
« Reply #2 on: November 04, 2009, 06:08:19 PM »
The main reason that this won't work is because a vertical tube entering through the bottom of the container isn't actually buoyant.  In order to float upwards, water must be able to move underneath whatever is supposed to float.


Cherryman

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Re: am i missing something obvious?
« Reply #3 on: November 04, 2009, 07:08:50 PM »
The main reason that this won't work is because a vertical tube entering through the bottom of the container isn't actually buoyant.  In order to float upwards, water must be able to move underneath whatever is supposed to float.

So if i put a piece of wood (or any other floating stuff)  straight on the bottom of a water holding compartment it will not fload up? 

Comassion

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Re: am i missing something obvious?
« Reply #4 on: November 04, 2009, 07:27:57 PM »
So if i put a piece of wood (or any other floating stuff)  straight on the bottom of a water holding compartment it will not fload up?

Even then, water can still slip between the bottom of the tank and the wood surface.  However, if you put a vertical wood rod through a correspondingly sized hole in the bottom of a water tank with just a little bit sticking out of the bottom, you'll see the wood rod drop through the bottom rather than float upward.

Cherryman

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Re: am i missing something obvious?
« Reply #5 on: November 04, 2009, 07:37:32 PM »
Even then, water can still slip between the bottom of the tank and the wood surface.  However, if you put a vertical wood rod through a correspondingly sized hole in the bottom of a water tank with just a little bit sticking out of the bottom, you'll see the wood rod drop through the bottom rather than float upward.

 

You stated when there can not come water underneath, there is no boyancy.

So i ask (theoretically)  If you have perfect smooth surface as a tank bottom and you press a perfect smooth  floating "something"  on it, it stays down?   

I would think there would still be buoyancy, i can imagine that there also will be vacuum or water pressure which can exceed the buoyancy, but that does not mean there isn't any bouncy..  ?

Its not an attack.. I just wondered .

Comassion

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Re: am i missing something obvious?
« Reply #6 on: November 04, 2009, 07:50:37 PM »
If you can indeed get two perfectly smooth surfaces that keep water from getting between them, then yes, you should be able to keep those two surfaces attached even if one of those surfaces belongs to an otherwise 'free floating' object.


Of note also is the fact that if you have two perfectly smooth surfaces touch, they will adhere to each other in any environment due to pressure - interestingly enough, even in a vacuum, due to pressure from virtual particles (The Casimir effect).


A more feasible way to see something like this in action would be to put a block of wood in the bottom of a dry tank, seal the bottom with some sort of watertight seal (though I'm not sure how to get a watertight seal that doesn't also otherwise attach the wood to the bottom - maybe you could use caulk, but not let it dry), and then fill the tank with water.  Even when the wood is submerged, as long as water can't get under the wood, it should remain on the bottom.

Cherryman

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Re: am i missing something obvious?
« Reply #7 on: November 04, 2009, 07:54:02 PM »
If you can indeed get two perfectly smooth surfaces that keep water from getting between them, then yes, you should be able to keep those two surfaces attached even if one of those surfaces belongs to an otherwise 'free floating' object.


Of note also is the fact that if you have two perfectly smooth surfaces touch, they will adhere to each other in any environment due to pressure - interestingly enough, even in a vacuum, due to pressure from virtual particles (The Casimir effect).

Now you mention it, i have heard of the Casmir effect indeed.

But my question remains..  Is there NO buoyancy, or do the "other" forces exceed the buoyancy?

Comassion

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Re: am i missing something obvious?
« Reply #8 on: November 04, 2009, 08:04:44 PM »
Now you mention it, i have heard of the Casmir effect indeed.

But my question remains..  Is there NO buoyancy, or do the "other" forces exceed the buoyancy?

There would be no upward buoyant force from the water, because buoyancy is effectively a type of pressure.  In order to exert said pressure on an object, the water has to be touching the object from the points at which it is exerting that pressure.  In the case we were talking about where you allow no water underneath your object, the buoyant force remaining (from the water above the object) is actually downward, and is holding the object against the smooth surface.

Cherryman

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Re: am i missing something obvious?
« Reply #9 on: November 04, 2009, 08:07:30 PM »
There would be no upward buoyant force from the water, because buoyancy is effectively a type of pressure.  In order to exert said pressure on an object, the water has to be touching the object from the points at which it is exerting that pressure.  In the case we were talking about where you allow no water underneath your object, the buoyant force remaining (from the water above the object) is actually downward, and is holding the object against the smooth surface.

Ok Tnx!


broli

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Re: am i missing something obvious?
« Reply #10 on: November 04, 2009, 08:08:11 PM »
1) use energy to create a water vortex in the tank
2) insert air filled object at bottom of vortex
3) extract as much energy back from water vortex
4) extract energy from air filled object moving up
5) compare input energy to output energy

If it works you would have done some very cool science, if it doesn't work you still would have done something not a single physics professor has thought of.

jadaro2600

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Re: am i missing something obvious?
« Reply #11 on: November 06, 2009, 04:53:11 AM »
using an electrode shaped like a ring at the bottom of the tank will create a vortex motion as the bubbles of the gas rise; the column creates upward  motion and in the center a vortex will eventually form.

Majority gas production should be at the lowest point, ..the height of the second electrode is variable...  a vortex WILL form, i've done this in a pool with a large circular set of pvc pipes with holes cut evenly in the bottom. ..i was not electrolyzing the water, just using an air compressor. ... it was an interesting swim.

« Last Edit: November 06, 2009, 06:07:55 AM by jadaro2600 »

Judges

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Re: am i missing something obvious?
« Reply #12 on: November 06, 2009, 02:12:41 PM »
broli
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Posts: 1153

  Re: am i missing something obvious?
« Reply #10 on: November 04, 2009, 08:08:11 PM »Quote 1) use energy to create a water vortex in the tank
2) insert air filled object at bottom of vortex
3) extract as much energy back from water vortex
4) extract energy from air filled object moving up
5) compare input energy to output energy

If it works you would have done some very cool science, if it doesn't work you still would have done something not a single physics professor has thought of.

Thank you.
Interesting,,,,,would notice first the funcunctionality of (3) above,or put otherwise,,am I missing something,,hmmmmmmmm,,,has anyone done the eloctrollyis thing?,,As a driller of oil wells (central texas),,, I am imediatly drawn to how much PSI over time,,,PVC should work,,,love to see a WORKING plan,,interesting indeed!

Good Morning America


Joe in Texas

wings

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Re: am i missing something obvious?
« Reply #13 on: November 06, 2009, 04:12:52 PM »
using an electrode shaped like a ring at the bottom of the tank will create a vortex motion as the bubbles of the gas rise; the column creates upward  motion and in the center a vortex will eventually form.

Majority gas production should be at the lowest point, ..the height of the second electrode is variable...  a vortex WILL form, i've done this in a pool with a large circular set of pvc pipes with holes cut evenly in the bottom. ..i was not electrolyzing the water, just using an air compressor. ... it was an interesting swim.



see the effect Head-on Collision of Two Vortex Rings:

http://serve.me.nus.edu.sg/limtt/#Video_Gallery

same as pulsing mobious coil on TPU