Coriolis effect

Jack

If the coriolis effect does not determine the direction in which water drains down a plug hole in different parts of the world then is it totaly random which way the water spins.

selfAdjoint

No, it's not totally random. The coriolis force is one of the forces acting on the water, but it's proprtional to speed and the sine of the latitude, so in most drain situations it's pretty small, and is swamped by the local forces arising from the shape of the basin, the previous motions of the water (conservation of angular momentum) and so on. It's all determinate and may possibly be chaotic, but it's not random.

Jack

What I meant was does water always drain a certain way in different parts of the world?

emu

Yes, water always drains the same way in the same hemisphere. I believe the effect is weakest at the equator but I'm not sure about that one.

Jack

Therefore my point is why? If the coriolis effect only effects large fluids such as hurricanes then why does water always drain the same way in the same hemisphere?

STAii

In smaller fluids, put the coriolis affect aside.
Now there are a big number of factors that will affect how the water drains (see selfAdjoint's post), if all those factors were re-made the same way in the experiment of water drain, then the water will drain exactly the same way.

I don't see how you are trying to connect the coriolis effect to this, the coriolis effect will be neglible and you can almost forget about it in similiar situations.

MrCaN

The coriolis effect doesn't determine the way a drain drains. And they don't drain the same way everywere on the hemisphere. Now most drains do drain the same way, because they are made the same way, that is they are all spun the same way when polished, producing grooves that determine the flow down the drain.

Jack

So do you mean it has nothng to do directly with position of the earths surface?

chroot

Not a thing.

- Warren

Jack

Surely that can't be true! So you could bring an Australian sink over to England and the water would drain the same way?[8)]

rdt2

It might, it might not. The point is that, on this scale, the Coriolis force is swamped out by other influences.

Cheers,

Ron.

Jack

I realise that now it's just i'm still confused firstly as to weather there realy is a difference between the direction in which water spins in the two hemispheres and secondly, if it does, why does it if it's not due to the coriolis effect?

chroot

Didn't this thread answer both of those questions in detail already?

- Warren

RuroumiKenshin

Does the corioulis force affect the way we think? electricity? the weather?

damgo

No, no, yes. Large-scale weather patterns are affected by the Coriolis effect: it causes cyclones to rotate in oppoosite directions in the two hemispheres; the trade winds around the Equator to bith point west; and the jet streams in both hemispheres to point east.

selfAdjoint

It is possible to make drains in lab conditions where all the other forces are minimised, and then the water drains according to what the coriolis effect says.

The coriolis effect is a force that acts on every moving thing. It is proportional to the speed and to the trigonometric sine of the latitude. It acts to the right if the velocity vector of the moving thing in the Northern hemisphere and to the left in the Southern hemisphere. But the effect is very weak, and it really shows up only when a lot of little things are all going the same way, as in air or ocean movements.

The effect of the sine dependence: There is no coriolis at the equator. It is half its maximum strength at 30^o latitude, 71% at 45^o, 87% at 60^o, and 100% at the poles.

damgo

For the record, the Coriolis force is given by

F = -2m(w x v)

where w=7.292e-5 /sec is the angular velocity of the Earth. So at the Equator, the Coriolis force vanishes for horizontal motion, but gives maximum deflection for vertical motion.

Roughly, this corresponds to a deflection of about 10 degrees/hour from a straight trajectory for a freely moving object around the middle of one of the hemispheres.