Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: alansm on 05/02/2009 18:26:54

Title: Water Down Plughole Poll to test this urban myth.
Post by: alansm on 05/02/2009 18:26:54: Quote from: Eric on 17/12/2008 20:46:44
Eric asked the Naked Scientists:

Does the water spinning in a toilet when flushed go in opposite directions in
the northern and southern hemispheres?

Lets find out!
Title: Water Down Plughole Poll to test this urban myth.
Post by: Vern on 05/02/2009 18:31:35: I ran a poll like this some time back. I kept getting dry lab results. Many folks feel so strongly that they know the answer that they won't do the test.

Dry lab: Reporting the results of an experiment without actually doing the experiment.
Title: Water Down Plughole Poll to test this urban myth.
Post by: lyner on 05/02/2009 18:43:40: Unfortunately you're looking for such a small effect and this poll is going to be affected, not only by the dry lab thing but the selective nature of your contributors. You may well get a significant vote against the predicted one because people who see it go the 'wrong' way may be more ready to report it than the ones who are not surprised by what they have seen.
Now, if you gave every contributor a fiver to produce a picture of the result . . . .
Cheers. Hic!

The toilet bowl / flush is probably the worst system to examine, in any case. The designs may well introduce some 'swirl' in any case so a brand leader would dominate. An emptying bath would be a bit fairer as a test.

Btw, I polled! So far so good - 100% for the theory.
Title: Water Down Plughole Poll to test this urban myth.
Post by: syhprum on 05/02/2009 19:27:26: I checked with my WC but no swirling is apparent so I have moved on to the hand basin, the first thing I noticed was that as it filled the incoming water introduced a strong counterclockwise swirl so I have returned to my keyboard to type this while it settles down and I am now returning to the bath room to pull the plug.
There was little swirling but it seemed to be anticlockwise so I will mark the poll thus.

Of course the spin direction will be the same (for large masses of air or water) in the north and south hemispheres it just looks different because down south you are inverted relative to the elliptic
I have also made this test in Brisbane and although the effect is small it also tends to swirl in the same direction relative to the Earths rotation.
i.e Apparently clockwise due to my head pointing south downunder
Title: Water Down Plughole Poll to test this urban myth.
Post by: Vern on 05/02/2009 19:40:24: Hey; we're actually getting wet lab results this time [:)] I suspect that the manufacture of the bowl would have a large effect on the swirl as someone already suggested. The results might be interesting this time.
Title: Water Down Plughole Poll to test this urban myth.
Post by: Chemistry4me on 24/03/2009 03:56:48: Seeing as alansm asked.

My toilet doesn't spin at all.
I think it must be the toilet. [:)]
Title: Water Down Plughole Poll to test this urban myth.
Post by: dlorde on 24/03/2009 14:48:03: This experiment has been done many times before. IIRC if any coriolis force is exerted on the water, it is overwhelmed by the shape of the container and/or the disturbances caused flushing, or pulling the plug, or movements in the water due to previous filling, convection, etc.
Title: Water Down Plughole Poll to test this urban myth.
Post by: syhprum on 25/03/2009 17:51:22: Should I be allowed two votes as I have observed the phenomena in both hemispheres?
Title: Water Down Plughole Poll to test this urban myth.
Post by: Mazurka on 27/03/2009 17:51:23: and me - i observed it in two sinks and it went different ways in each one [:o]
Title: Water Down Plughole Poll to test this urban myth.
Post by: yor_on on 27/03/2009 20:18:25: Ok, it doesn't care really.
It just flows accordingly to what forces work on it.
And it doesn't care for any 'preconceptions' :)
Title: Water Down Plughole Poll to test this urban myth.
Post by: Chemistry4me on 28/03/2009 08:18:59: Although if you watched one particular episode of the Simpsons you would be tempted to think otherwise.
Title: Water Down Plughole Poll to test this urban myth.
Post by: Chemistry4me on 28/03/2009 12:59:16: What were you about to say Mr. yor_on? [:)]
Title: Water Down Plughole Poll to test this urban myth.
Post by: lyner on 28/03/2009 17:05:04: I think he has trouble spelling corioiorlilis.