Students will then notice how the water ends up swirling down the drain in the same direction that they stirred it earlier. Repeat the experiment stirring counterclockwise.
Students should conclude that the water swirls down the drain in the same direction that it was initially moving. Do you have extra time to fill? Ha ha. If so, repeat the investigation waiting longer after stirring for the water to settle. Thus even the slightest, imperceptible movement will get amplified into fast swirling. The reason this happens is the same as why a spinning ice skater will spin faster as she pulls in her arms and legs see Figure 3.
It has to do with a quantity known as angular momentum. The angular momentum is the product of three quantities: the mass of the object, the size of the object, and the spinning speed.
For an object moving around in a circle, like a ball on a string being twirled around, the size in this case would refer to the distance of the ball from the center of the circle, i. Keep that in mind when we get back to the swirling water.
One last bit of terminology: When something stays the same, scientists say it is conserved. So the idea that the angular momentum stays the same is known as the conservation of angular momentum.
Ask students: When the spinning ice skater starts to pull in her arms and leg, which of those change and which stay the same? Does her mass change? Does her size change? Suppose excluding units for now , that the mass, size, and speed have these values:. What happens to her speed? These sideways deflections are attributed to the Coriolis force, although there really is no force involved--it is just an effect of being in a rotating reference frame.
The circulation directions result from interactions between moving masses of air and air masses moving with the rotating earth. The effects of the rotation of the earth are, of course, much more pronounced when the circulation covers a larger area than would occur inside your bathtub. Even in a tub having a perfectly symmetric drain, the circulation direction will be primarily influenced by any residual currents in the bathtub left over from the time when it was filled.
It can take more than a day for such residual currents to subside completely. If all extraneous influences including air currents can be reduced below a certain level, one apparently can observe that drains do consistently drain in different directions in the two hemispheres. Finally, Thomas Humphrey, a senior scientist at the San Francisco Exploratorium, discusses in more detail the reasons why we do not see the Coriolis effect at work in the bathroom:.
For a fee, they will allegedly demonstrate that the toilets flush in opposite directions. It is only for show, however; there is no real effect. Yes, there is such a thing as the Coriolis effect, but it is not enough to dominate the flushing of a toilet--and the effect is weakest at the equator.
Coriolis acceleration at mid-latitudes is about one ten-millionth the acceleration of gravity. Because it is a very small acceleration, it needs a very long distance for it to produce an appreciable curvature--and hence directionality--to the motion. A toilet or sink is just not large enough.
The Coriolis force tends to make things on the surface of the object to spiral a certain direction. As the earth rotates, this motion causes everything on the surface to experience the Coriolis force, including the water in your sink. But, the Coriolis force is so weak that it doesn't really do anything until it acts on a lot of material.
Your sink simply does not have enough water to be affected by the Coriolis force. What a retarded experiment!!! Everything that is measured on the earth is taken from the surface, looking at the surface and is measured for that particular area, not from above and below. Kirsty , Leeds, England" Kirsty girl, please don't become something that has anything to do with science or physics.
Maybe think on the lines of I don't know, housewife? Just e3liminate the problem of sink and plug hole issues and just pour the water people!! No one said anything about what happened to the water at the poles. I came into some money and, having nothing better to do, I took a cruise to Antartcia and managed to catch a ride to a camp very close to the South pole.
I took along a flat wash basin that had a hole and a rubber plug in it. I filled it about half full and took it outside so it would not be influenced by structural or gravitational fields of the buildings. I carefully pulled the plug and watched. Unfortunately the water froze before it could drain out so I guess this is why the effect is only seen at or near the equator.
Land Waylamd, Chino. California ISA When you get drunk which way the room is spinning? Seriously now, I think the water is just random, but is true for the tornados. The north hemisphere the tornados are spinning counter clockwise and on south hemisphere the tornados are turning clockwise.
Dan the man, Bucharest Romania Unbelievable. The vortex only occurs when the water level is low so should in effect do the same to your half finished cup of tea. It doesn't because the force while exists is not strong enough. People have talked of physics and shapes of bowl etc but nobody mentioned the real force of the waste pipe. Unromantic as it may be the swirl of a plug hole is simply due to the way the waste pipe is configured explaining the phonomenem of hand swirled sinks turning the other way.
When you empty a bath there is no vortex as the pipe is full due to the pressure of the water. Only when the pressure reduces due to the volume of water does a swirl appear the direction of which depends on the shape of the pipe below.
Think not what you are told but what is physically happening otherwise you will end up stood on the equator listening to a charlatan with a bucket. The effect of draining amplifies small movement as the water moves to the centre the same way a ballet dancer increases spin speed by putting arms in. Any chaotic system can be influenced by tiny changes, The butterfly effect. Other effects such as basin shape may be larger but over a large number of tests on different set ups random factors should cancel out leaving any small consistant factor to show a measurable majority, or of course the most popular basin design could tip the balance.
Steve Turner, Witham, Essex I have spent the last 15 years exploring this phenomena on a full time basis and I can now give the definitive answer. Ideally one should consume a kebab prior to urination. I hope this answers the question once and for all.
Baz l'hommedeleau, London UK Wow people, just wow. Some answers are way out there. Others are so convoluted that it's beyond reasoning. Only one person has come close to a logical answer to the apparent 'different' direction.
Simple answer, the direction is the same, it's only the viewers point of observation that changes. Anti-clockwise spin when viewed from the southern hemisphere, appears as a clockwise spin when viewed from the northern hemisphere.
And guess what, vice versa applies regardless of the spin direction. Think about it, devise a simple test for yourself using you eyeline as the 'equator', test it for yourself, and prove to yourself it's simply your view perspective that 'changes' the direction, not the direction of spin suddenly stopping at the equator, and then miraculously reversing itself.
Paul Nankervis, Perth Australia I've studied this with many different tubs, kitchen sinks, bathroom sinks for many many hours with over a hundred tests and I concluded that what hemisphere you're in has nothing to do with the direction of the spin.
Joe Vortex, Montreal, Canada This is a common myth, and the previous comments settle it quite well. I only wish to add that the size or distance needed for Coriolis to have an noticeable effect is 10kms Natassia Day, Perth, Australia Having read most of the above I am thinking of how to exploit this feature.
My current interest is in making, as a hobby, a water wheel electric power generator. There are of course hundreds of examples, the one that interests me is a backpack model, a tube to be inserted into a flow of water and to produce campsite lighting.
My version could be called the Downunder increasing pitch screw turbine. The downunder because I am in the southern hemisphere and of course the water flows opposite that of the northern types, it looks like that idea is a no go. The whole thing, alternator and all about 3 ft long and 6 inches in diameter, it would be contained with ropes tied to trees, rocks, a bridge or whatever.
I then went immediately upstairs and flushed that toilet and it went clockwise. My downstairs and upstairs are in the same hemisphere. Why did they not rotate in the same direction? Why doesn't the bath water spin increasingly fast in the first place if left to sit for days? I'm with the "Definitely has an effect, but it's probably of mathematically insignificant magnitude when compared to 'other' factors.
Unless you happen to be a ocean sized lump of atmosphere with nothing else better to do" side. Coriolis force is in effect with this phenomenon. Under strict lab environment, it is always counterclockwise in the northern hemisphere. As a matter of fact, in a random household environment, a high percentage of the results is counterclockwise in the northern hemisphere.
But due to other forces such as sink design, initial spin, there are some cases where a small percentage go wrong. So basins were just 2 standard sizes, facilitating a controlled experiment. In 5 of the 7 basins I tested, the direction was anti-c, in the other 2, clockwise.
That would strongly support the 'random' opinion, except for the fact that I tested each basin three times, getting the same result on all replications. I feel this reduces the 'random' case. Btw, lets not make ad hominem comments in our discussions. As an oldie am often accused of Luddism, but blogs like this really do help the world go roind, if I can use the expression!!
Mike, Oxford UK The water that goes down the plughole spin counter-clockwise due to the fact that the Earth spins that way. Glad to be of any help! Drill the screw through a board. Drill it from the top and look at the bottom. If you look from the top it spins right, but looking from the bottom it's backwards. Imagine a screw through Earth and the Sun is the power drill. It's powered by the sun and forced by the Earth's axis. Love, learning and feedback is appreciated. There is a Coriolis Effect that we can see in the hurricanes and Typhoons that spin in opposite directions.
They cannot be sustained crossing the equator because of this Coriolis Force. However, the same force is so weak at the level of the water flowing down your drain, that many other factors overwhelm it. At the scale of the weather, there aren't as many other forces that can match the Coriolis.
As a hurricane moves away from the equator, it is often overwhelmed by the Upper Atmosphere Jet Stream winds, but around the equator in open water this force is what is generating the rotation of the rising vapors, which become the hurricane. When the hurricane moves over the land the uprising vapors diminish and there is more distortion in the other winds, which soon kill the hurricane.
Good thing for us land dwellers. Probably just as unlikely as the coriolis effect! Stop talking about it and just try the experiment! It's random! Get your heads out of your toilets, people.
Chris Saxby, London Ontario Good grief.
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