## natural phenomenon

hi...

we see this phenomenon in our everyday lilfe...

in a sink, if we open its hole suddenly, the water gushes toward it in circular manner and not directly...

why the water has to first circle the hole and then it passes through the hole...why it never takes the shortest route to go through the hole.....

pls clarify..
 Blog Entries: 27 Recognitions: Gold Member Homework Help Science Advisor hi surabhi! welcome to pf! it depends which way you pull the plug out  it's almost impossible to pull it out vertically or radially (ie without any clockwise our anticlockwise motion)  so when you pull the plug, you're actually stirring the water by doing so  the water will continue to flow down the plughole the way you stirred it!

 Quote by tiny-tim hi surabhi! welcome to pf! it depends which way you pull the plug out  it's almost impossible to pull it out vertically or radially (ie without any clockwise our anticlockwise motion)  so when you pull the plug, you're actually stirring the water by doing so  the water will continue to flow down the plughole the way you stirred it!
So theoretically if I mechanically prevent the plug to rotate while pulled (press fit it to a guiding tube etc..) there won't be any vortex at the sink?

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## natural phenomenon

 Quote by GT1 So theoretically if I mechanically prevent the plug to rotate while pulled (press fit it to a guiding tube etc..) there won't be any vortex at the sink?
I've never heard of this "we create the vortex when pulling the plug" idea, not sure how true it is.

The vortex created is one of the most efficient ways for water to travel down the hole.

If you take a 2 litre bottle, fill it with water and turn it upside down, it will glug out as the air is sucked in. If you do the same thing but rotate the bottle gently, you will create the vortex which will allow the water to empty smoothly whilst allowing the air in.

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 Quote by jarednjames I've never heard of this "we create the vortex when pulling the plug" idea, not sure how true it is.  If you do the same thing but rotate the bottle gently, you will create the vortex which will allow the water to empty smoothly whilst allowing the air in.
Exactly! You create the vortex by giving the water an initial rotation

you decide whether it's clockwise or anti-clockwise!

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 Quote by tiny-tim Exactly! You create the vortex by giving the water an initial rotation  you decide whether it's clockwise or anti-clockwise!
With a bottle yes, because I'm spinning it.

But I just spent ten minutes pulling the plug and couldn't change the direction of rotation as you describe.

I can understand how it may affect things, but my bathroom sink has a mechanical plug (you operate a lever to open the plug - no contact with it - the plug doesn't rotate at all when pulled) and the water still rotates.

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 Quote by jarednjames  my bathroom sink has a mechanical plug (you operate a lever to open the plug - no contact with it - the plug doesn't rotate at all when pulled) and the water still rotates.
since we're into experimental physics here
does it rotate the same way every time?
(and does it make any difference whether you originally filled the sink from the left or the right tap/fawcet?)

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 Quote by tiny-tim does it rotate the same way every time?
No, this one actually surprised me. Mostly always went anti-clockwise but twice it went clockwise.
 (and does it make any difference whether you originally filled the sink from the left or the right tap/fawcet?)
Central mixer tap directly over the plug.

I can't believe I'm doing this, what a way to spend a Saturday.

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 Quote by jarednjames No, this one actually surprised me. Mostly always went anti-clockwise but twice it went clockwise. Central mixer tap directly over the plug.
Well, it certainly isn't trying to do straight down, and if it goes either way, then surely it must be the initial conditions?
 I can't believe I'm doing this, what a way to spend a Saturday.
Could you possibly post a video of it?

And have you used a spirit-level to check that the sink is perfectly level?

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 Quote by tiny-tim Well, it certainly isn't trying to do straight down, and if it goes either way, then surely it must be the initial conditions?
Well it's what I'm inclined to think, but then what would change those conditions in a mechanical setup? I suppose I'm over thinking it, looking at the sink/drain design instead of your own motion.
 Could you possibly post a video of it?
Yes, I'll immortalise my exciting home life.
 And have you used a spirit-level to check that the sink is perfectly level?
I installed it, how dare you insinuate my handy work is shoddy!

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 Quote by jarednjames Well it's what I'm inclined to think, but then what would change those conditions in a mechanical setup? I suppose I'm over thinking it, looking at the sink/drain design instead of your own motion.
hmm  if the plug doesn't come up exactly straight (say if it leans slightly towards two o'clock), it will create a flow within the sink even before there's a hole

since the sink isn't symmetric, that flow will be rotational
 Yes, I'll immortalise my exciting home life.

leave your public wanting more, and you'll be able to bring out a sequel!

maybe about whether the light goes out when you close the fridge?
 I installed it, how dare you insinuate my handy work is shoddy!
even in Vegas, they re-check the equipment every day
oooh  if you set up a webcam, you can take bets on which way it will go next time!

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 Quote by tiny-tim hmm  if the plug doesn't come up exactly straight (say if it leans slightly towards two o'clock), it will create a flow within the sink even before there's a hole  since the sink isn't symmetric, that flow will be rotational
That's what I'm thinking at the moment.
 just the bathroom, please  leave your public wanting more, and you'll be able to bring out a sequel!

 maybe about whether the light goes out when you close the fridge?
Just to re-enforce how exciting things are....

In my first year of uni we 'tested' this whilst a bit drunk. We emptied the fridge in the uni halls and one of my flat mates climbed in (small Chinese dude).
 even in Vegas, they re-check the equipment every day oooh  if you set up a webcam, you can take bets on which way it will go next time!

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