stupid question but ...........

[Hoppy]

Why does the water go down the plughole in different directions in the two hemisphere's ??

 

[Far_X]

coz it just does!!!

 

[The Kraken]

Because of the equator. The same reason that waves go off the bow of a boat in different directions.

 

[Firefyter]

Why does the water go down the plughole in different directions in the two hemisphere's ??

It's called the Coriolis Effect, or the Coriolis Force. You can google it for more info.......

 

[Hoppy]

It's called the Coriolis Effect, or the Coriolis Force. You can google it for more info.......

Or maybe not as the case maybe for when you do google it you find the following :-

extracted from here

Compared to the rotations that one usually sees (tires on a travelling automobile, a compact disc playing music, or a draining sink), the rotation of the Earth is very small: only one rotation per day. The water in a sink might make a rotation in a few seconds and so have a rotation rate ten thousand times higher than that of the Earth. It should not be surprising, therefore, to learn that the Coriolis force is orders of magnitude smaller than any of the forces involved in these everyday spinning things. The Coriolis force is so small, that it plays no role in determining the direction of rotation of a draining sink anymore than it does the direction of a spinning CD.

The direction of rotation of a draining sink is determined by the way it was filled, or by vortices introduced while washing. The magnitude of these rotations may be small, but they are nevertheless gargantuan by comparison to the rotation of the Earth. I decided to include a picture of a draining sink, and the first one I tried in my house was found to drain clockwise (the opposite of what the silly assertions would have it do here in the northern hemisphere). This direction was determined entirely by the way the tap filled the sink. The direction of rotation of a draining toilet is determined by the way the water just under the rim is squirted into the bowl when it is flushed.

 

[Tobagoman]

I'm not sure about the Coreolis affect on small systems like drains, but in and over the ocean, both atmospheric and ocean currents are affected greatly by this phenomenon.
That is why in the Northern Hemisphere storm systems rotate in a counter-clockwise rotation.
Without getting into all the physics, here is a down and dirty quick laymens reason;
The earth is spinning counter-clockwise when looking down from the north pole. Take a ruler and spin it about its axis, the center is moving alot slower than the outside edges. This is the same for the higher lattitudes on earth (which spin slowly) compared to the equater which has a higher velocity. Due to friction this causes the counter-clockwise movement (think about putting a finger against each side of a baseball and move them forward, one faster than the other, this will impart spin on the ball) of atmospheric and ocean systems (along with the heating and cooling that causes verticle movements).

I can't be sure that this force could impart spin on such a small scale as a drain, but I could be wrong.

 

[Walter]

Actually, the Coreolis effect does impact drains, but to see it, you have to left the water sit motionless for days. The force is so small that other factors overpower it.

 

[Firefyter]

Actually, the Coreolis effect does impact drains, but to see it, you have to left the water sit motionless for days. The force is so small that other factors overpower it.

This is exactly they way I was taught.....

 

[H2Andy]

actually, after much thought, i conclude as follows:

the top of the earth rotates counter-clockwise, which makes the drains go backwards
and drain clockwise

conversely, the BOTTOM of the earth MUST rotate clockwise in order for the drains to drain counter-clockwise

(or vice-versa, it really doesn't matter)

which leads me to conclude, and i beilieve i am unanimous in this, that the earth is
really split at the equator, with the top (or bottom) spinning left (or right) and the
bottom (or top) spinning right (or left).

this is why hurricanes and cyclones form. all that rotating creates fiction down
there (ahem...) thus spawning weather systems with a grudge against Florida
(or Malasya).

or.... all of this crap is wrong, and you can find drains that go clockwise and counter-clockwise in both hemispheres:

http://www.loc.gov/rr/scitech/mysteries/coriolis.html

 

[Lightning Fish]

Or maybe not as the case maybe for when you do google it you find the following :-

extracted from here

Compared to the rotations that one usually sees (tires on a travelling automobile, a compact disc playing music, or a draining sink), the rotation of the Earth is very small: only one rotation per day. The water in a sink might make a rotation in a few seconds and so have a rotation rate ten thousand times higher than that of the Earth. It should not be surprising, therefore, to learn that the Coriolis force is orders of magnitude smaller than any of the forces involved in these everyday spinning things. The Coriolis force is so small, that it plays no role in determining the direction of rotation of a draining sink anymore than it does the direction of a spinning CD.

The direction of rotation of a draining sink is determined by the way it was filled, or by vortices introduced while washing. The magnitude of these rotations may be small, but they are nevertheless gargantuan by comparison to the rotation of the Earth. I decided to include a picture of a draining sink, and the first one I tried in my house was found to drain clockwise (the opposite of what the silly assertions would have it do here in the northern hemisphere). This direction was determined entirely by the way the tap filled the sink. The direction of rotation of a draining toilet is determined by the way the water just under the rim is squirted into the bowl when it is flushed.

Hoppy, you've got the answer. I asked a Professor of fluid dynamics this question and he basically gave the above answer. He also included pipe and connections and the inability to perfectly place the outlet in the center of the bowl, sink, tank as another cause of the rotation. The bowl, tank, (whatever) would also have to be perfectly symmetrical.

If a tank of water and all pipe and connections were perfectly aligned with the outlet perfectly centered and there were no other disturbances, then the effect of the rotation of the earth would be noticeable.

Cheers,
Bill.