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-   -   who knows the correct answer? (http://www.travelbanter.com/showthread.php?t=39638)

Peter Webb August 22nd, 2004 09:17 AM

who knows the correct answer?
 

"maxi" wrote in message
...
is it true that if you put water in a sink and pull the plug, the water
turns the oposite way as in the northern hemisphere?

we made a bet and would like to know the correct answer!

thx for the help.

Max



Unless your bath is huge - hundreds of metres wide - and extremely still
with no waves or turbulence at all - it will be random.




maxi August 22nd, 2004 09:26 AM

so there is no difference in the turning direction between the northern and
southern hemisphere?




"Peter Webb" schreef in bericht
...

"maxi" wrote in message
...
is it true that if you put water in a sink and pull the plug, the water
turns the oposite way as in the northern hemisphere?

we made a bet and would like to know the correct answer!

thx for the help.

Max



Unless your bath is huge - hundreds of metres wide - and extremely still
with no waves or turbulence at all - it will be random.






Ralph Holz August 22nd, 2004 10:14 AM

Hi,

so there is no difference in the turning direction between the northern and
southern hemisphere?


Yes, there is. It does turn the other way round.

Ralph

Road_Hog August 22nd, 2004 10:26 AM


"maxi" wrote in message
...
so there is no difference in the turning direction between the northern
and
southern hemisphere?


Yes, but as the reply said all other factors would have to be taken out of
the equation. In reality this doesn't happen.

"Bathwater should drain anticlockwise in the northern hemisphere, clockwise
in the southern and straight down at the equator. This is caused by the
Coriolis force, a result of the earth's eastward rotation, which in the UK
causes water north of the plug to run to the western edge of the hole, while
water on the opposite side of the plug moves to the eastern edge, producing
an anticlockwise vortex. In Australia, the water should move in the opposite
direction.
However, the direction of the vortex is easily disturbed by currents in the
water, the alignment of the plughole, the shape of the bath, or water
temperature, so the phenomenon is difficult to observe."

And a little more detail.

"If you had a perfectly smooth bathtub in a perfectly round shape, and you
filled it full of water, let the water sit for a few days (to let every
last bit of turbulence from the filling of the bathtub die out), and then
let the water drain though a single hole in the middle of the bathtub,
then the water would begin to circulate (counter-clockwise in the northern
hemisphere, and clockwise in the southern hemisphere). This is exactly
what happens with weather systems. A low-pressure system is just like
this ideal bathtub - air is rushing in to the middle of the low pressure
system to try and fill the low pressure area, and water is rushing in
toward the drain to try and fill it.


However, bathtubs and toilets do not have these perfect shapes, and the
direction that the water circulates is determines by the shape of the
bathtub or by any turbulence that may be present from filling the bathtub.
The Coriolis forces are swamped by any minor imperfections.


It is possible to estimate the Coriolis forces in a bathtub. If we have a
bathtub at the North Pole (where Coriolis forces would be greatest, so
assume it is a hot tub so it doesn't freeze), and the bathtub is one meter
in radius, and the water drains from the edge of the bathtub to the drain
at the center in one second, then the deflection of the water will be less
than approximately 0.05 millimeters. This would be measurable, but is
rather tiny, and definitely nowhere near the circulation seen in most
bathtubs. A larger bathtub or a faster draining rate would amplify the
deflection.


In short, any "experiment" purporting to show the Coriolis effect in a
bathtub, toilet, or pan of water is a fraud, although not necessarily
intentional. But a glance at a satellite picture of clouds shows true
Coriolis effects without the need for a hottub at the North Pole!"



HTH








A Mate August 22nd, 2004 10:53 AM

Who Cares!!?




"maxi" wrote in message
...
is it true that if you put water in a sink and pull the plug, the water
turns the oposite way as in the northern hemisphere?

we made a bet and would like to know the correct answer!

thx for the help.

Max





Ralph Holz August 22nd, 2004 11:11 AM

Who Cares!!?

You're from QLD, right? ;-)

Ralph

Ralph Fox August 22nd, 2004 12:22 PM

On Sun, 22 Aug 2004 07:58:27 GMT, in message
, maxi wrote:

is it true that if you put water in a sink and pull the plug, the water
turns the oposite way as in the northern hemisphere?

we made a bet and would like to know the correct answer!

thx for the help.



The water turns clockwise here in the southern hemisphere[*].

Which way does the water turn in the northern hemisphere?
Clockwise or anticlockwise? Is it true that it turns the
opposite way as in the southern hemisphere?


[*] That's what the coriolis force wants it to do.
However, any existing currents in the water [â€*] will
almost always have a greater effect.

[â€*] Any existing currents great enough to cause the water to travel
around in the sink more than once every 24h x cosec(latitude)
will have a greater effect.

When you fill the sink, it will have small currents greater than
this. You'll have to wait a long time for the currents to stop.

When you put your hand in the water to grab the plug,
you'll create currents greater than this (and mess up the test).



--
Cheers,
Ralph

How To Ask Questions The Smart Way: http://www.catb.org/~esr/faqs/smart-...ns.html#before

maxi August 22nd, 2004 01:32 PM

that is what i call a clear answer!

Thx, I lost my bet :)


"Road_Hog" schreef in bericht
...

"maxi" wrote in message
...
so there is no difference in the turning direction between the northern
and
southern hemisphere?


Yes, but as the reply said all other factors would have to be taken out of
the equation. In reality this doesn't happen.

"Bathwater should drain anticlockwise in the northern hemisphere,

clockwise
in the southern and straight down at the equator. This is caused by the
Coriolis force, a result of the earth's eastward rotation, which in the UK
causes water north of the plug to run to the western edge of the hole,

while
water on the opposite side of the plug moves to the eastern edge,

producing
an anticlockwise vortex. In Australia, the water should move in the

opposite
direction.
However, the direction of the vortex is easily disturbed by currents in

the
water, the alignment of the plughole, the shape of the bath, or water
temperature, so the phenomenon is difficult to observe."

And a little more detail.

"If you had a perfectly smooth bathtub in a perfectly round shape, and you
filled it full of water, let the water sit for a few days (to let every
last bit of turbulence from the filling of the bathtub die out), and then
let the water drain though a single hole in the middle of the bathtub,
then the water would begin to circulate (counter-clockwise in the northern
hemisphere, and clockwise in the southern hemisphere). This is exactly
what happens with weather systems. A low-pressure system is just like
this ideal bathtub - air is rushing in to the middle of the low pressure
system to try and fill the low pressure area, and water is rushing in
toward the drain to try and fill it.


However, bathtubs and toilets do not have these perfect shapes, and the
direction that the water circulates is determines by the shape of the
bathtub or by any turbulence that may be present from filling the bathtub.
The Coriolis forces are swamped by any minor imperfections.


It is possible to estimate the Coriolis forces in a bathtub. If we have a
bathtub at the North Pole (where Coriolis forces would be greatest, so
assume it is a hot tub so it doesn't freeze), and the bathtub is one meter
in radius, and the water drains from the edge of the bathtub to the drain
at the center in one second, then the deflection of the water will be less
than approximately 0.05 millimeters. This would be measurable, but is
rather tiny, and definitely nowhere near the circulation seen in most
bathtubs. A larger bathtub or a faster draining rate would amplify the
deflection.


In short, any "experiment" purporting to show the Coriolis effect in a
bathtub, toilet, or pan of water is a fraud, although not necessarily
intentional. But a glance at a satellite picture of clouds shows true
Coriolis effects without the need for a hottub at the North Pole!"



HTH










AlmostBob August 22nd, 2004 04:59 PM

Quite simply Yes, and though small the coriolis force is the only force not
acting vertically on the water so the effect is demonstrable visible and
consistent. any answers received to the contrary regarding fraud are simply
the result of ignorance

--

"maxi" wrote in message
...
| is it true that if you put water in a sink and pull the plug, the water
| turns the oposite way as in the northern hemisphere?
|
| we made a bet and would like to know the correct answer!
|
| thx for the help.
|
| Max
|
|



www.poms.co.uk August 24th, 2004 10:08 PM


"maxi" wrote in message
...
is it true that if you put water in a sink and pull the plug, the water
turns the oposite way as in the northern hemisphere?

we made a bet and would like to know the correct answer!

thx for the help.

Max



Yep thats right







www.poms.co.uk





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