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Author Topic: Why does my tea bag always turn clockwise when removed from my mug?  (Read 5727 times)

Offline raineywoods

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I notice when I remove my tea bag after steeping it in a cup of water, it always spins in a clockwise fashion.  Does anyone know the physics behind this reaction?
« Last Edit: 06/12/2014 00:21:04 by chris »


 

Offline Bored chemist

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Re: Rotation of a Tea Bag
« Reply #1 on: 26/11/2014 19:59:22 »
That's the way the string is twisted?
 

Offline Notso

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Re: Rotation of a Tea Bag
« Reply #2 on: 02/12/2014 18:06:07 »
Check with an unused teabag - if they still spin clockwise then that's just a product of the manufacturing process. If not, then I expect it comes from a habit you have in the way you pour the water from the kettle into the mug.

Having just made a cuppa myself, I suspect that it is an artifact of habit. Personally I am right-handed, and the most accurate way to make sure I don't spill the water is to pour it into the opposite side from me, which results in an anticlockwise rotation of the water as I fill the mug, so naturally the bag unwinds clockwise.
« Last Edit: 02/12/2014 18:35:30 by Notso »
 

Offline Bill S

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Re: Rotation of a Tea Bag
« Reply #3 on: 02/12/2014 19:32:28 »
Quote
Check with an unused teabag

They rarely rotate significantly until wet.

Quote
which results in an anticlockwise rotation of the water as I fill the mug, so naturally the bag unwinds clockwise.

Not if the teabag is resting against the side or bottom of the mug. 

I'm still with Bored Chemist on this.

BTW, as someone who rarely uses teabags with strings, my mental image on reading the OP was of a teabag being spooned out of a mug and gyrating on the spoon.  I suspect that would have lead to a lively thread.  ;D
 

Offline Notso

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Re: Rotation of a Tea Bag
« Reply #4 on: 04/12/2014 13:52:52 »
They rarely rotate significantly until wet.

Then soak a teabag in hot water (while preventing its rotation) to prove that it's not being wet that causes the rotation somehow?

Quote
Not if the teabag is resting against the side or bottom of the mug.

I find that generally the water has sufficient angular momentum to lift the teabag and cause it to rotate with the water, even in such a case as you describe.
 

Offline lightarrow

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<<Why does my tea bag always rotate clockwise...>>

Answer: because it's a "tea time" bag  :)

--
lightarrow
 

Offline Arrual

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It also occurs with the drainage of water in a toilet bowl. It either depends on the manufacturer or which side of the equator you are on.
 

Offline RD

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It also occurs with the drainage of water in a toilet bowl. It either depends on the manufacturer or which side of the equator you are on.

That's an urban myth ...
Quote from: wikipedia.org/wiki/Coriolis_effect
  ... no consistent difference in rotation direction between toilet drainage in the Northern and Southern Hemispheres can be observed...
http://en.wikipedia.org/wiki/Coriolis_effect#Draining_in_bathtubs_and_toilets
 

Offline PmbPhy

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It also occurs with the drainage of water in a toilet bowl. It either depends on the manufacturer or which side of the equator you are on.
As RD explained, that's a common misconception. It's based on the assumption that it's caused by Coriolis forces acting on the water. The fact is that it's due to things such as the direction in which water leaves your toilet and the shape of the bowl and the angle at which the liquid initially enters that bowl. If there was a container of water which had a hole at the bottom which was simply "unplugged" with no rotation acting during the unplugging then there's no way to determine which way it will rotate, if it rotates at all. It might rotate according to the Coriolis effect but the effect is miniscule to have a large effect on the direction of direction of the water.
 

Offline Arrual

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It also occurs with the drainage of water in a toilet bowl. It either depends on the manufacturer or which side of the equator you are on.

That's an urban myth ...
Quote from: wikipedia.org/wiki/Coriolis_effect
  ... no consistent difference in rotation direction between toilet drainage in the Northern and Southern Hemispheres can be observed...
http://en.wikipedia.org/wiki/Coriolis_effect#Draining_in_bathtubs_and_toilets [nofollow]
It also occurs with the drainage of water in a toilet bowl. It either depends on the manufacturer or which side of the equator you are on.
As RD explained, that's a common misconception. It's based on the assumption that it's caused by Coriolis forces acting on the water. The fact is that it's due to things such as the direction in which water leaves your toilet and the shape of the bowl and the angle at which the liquid initially enters that bowl. If there was a container of water which had a hole at the bottom which was simply "unplugged" with no rotation acting during the unplugging then there's no way to determine which way it will rotate, if it rotates at all. It might rotate according to the Coriolis effect but the effect is miniscule to have a large effect on the direction of direction of the water.
Thanks for the clearification.
 

Offline PmbPhy

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Quote from: Arrual
Thanks for the clearification.
My pleasure! :)
 

Offline Bill S

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Update to the OP:  Twinings Spicy Chai tea bags rotate anti-clockwise! ;D

 

Offline jccc

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Update to the OP:  Twinings Spicy Chai tea bags rotate anti-clockwise! ;D

That's a great find! Only spend about 4 months.
 

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