Water in a bath tub, does it turn a different way?

Question

Depending on where your country is (north or south of the equator), does the water in a bath tub turn a different way when it goes down a plug hole. Why does this happen?

Answer 1

1. It's true for very large-scale phenomena like weather patterns that there's a difference between the motions in the two hemispheres. For example, the so-called Trade Winds curve in a different direction, due to the operation of what physicists call the Coriolis effect.

(The Coriolis effect is an apparent, sideways deviating "force" found when referring motion to a rotating frame of reference, in this case the "natural frame" for us to use, one tied to the Earth's own rotation. The effect is proportional to the vector cross product of the motion vector relative to earth's rotating surface, v, and Earth's spin vector, omega. This "pseudo-force" ultimately derives from taking PART of the full expression for acceleration in inertial space (but referred to rotating axes), and moving it to the other side of Newton's 2nd Law of Motion. After moving to the "Force side of the equation," that sundered limb from the original inertial totality appears as a mysterious and very personal sideways "force" : - 2 m (omega) X (v), or + 2 m (v) X (omega). "Centrifugal force" has a similar origin; both terms really arise from the negative of a dismembered part of inertial acceleration as viewed in a rotating frame.)

2. Getting back to your specific question : NO, it's not true for bathtubs. Anyone who tells you that it is is just subscribing to an old wives' tale, or international urban myth. Some scientists and applied mathematicians, led by the English astrophysicist Donald Lynden-Bell, did some controlled experiments on this two or three decades ago. They found that on the scale of the bathtub, other factors like the placement of the taps (faucets), irregularities in the tub's surface, whether the water had been stirred one way or the other (even HOURS ago), etc. were much more important in determining which way the water would flow into the plug hole, than simply whether they were north or south of the equator.

So let's give that old canard a decent burial.

Live long and prosper.

Answer 2

The coriolis effect is caused by the rotation of the earth about its axis. It gives a rotation of one revolution per day.

It affects large systems such as high and low pressure systems and even mesoscale systems such as the sea breeze and thunderstorms - which is why the rotation of tornadoes is different in each hemisphere. In small systems, however, such as dust devils and water going down plugholes, other factors (such as currents in the bathtub) are much stronger than coriolis and the rotation is in either direction in either hemisphere.

Coriolis is proportional to the sine of the latitude so it is zero at the equator and at a maximum at the pole. Water still spirals down the plughole on the equator when there is no coriolis effect at all.

In high latitudes if you had a tank large enough and the water still enough and you removed the plug carefully so that the water was not disturbed, coriolis could cause the rotation of the water as it flowed through the hole to favour a particular direction but in normal cases, water goes down whichever way it wants to.

Answer 3

You are correct, water leaving through the plug hole of a bath tub does swirl in opposite directions, depending on whether you are in the Northern or Southern hemisphere. This is caused by a phenomenon called "Coriolis Effect", which is caused by Earth's rotation, as someone else kindly has pointed out.

Answer 4

No. Its a persistent myth.

The Coriolis effect is far too small to affect anything much smaller than a country or continent. So it affects the weather and ocean currents, but has no effect on things even the size of the Great Lakes.

Answer 5

counting on the valve MFG. ie:Moen. single handle there's a bite of previous solder caught interior the nice and comfortable water port or the rubber seal has come aside and cloged the port..close the nice and comfortable water off to the homestead and open the backside valve to empty the water from the pipe..do away with the middle screw on the handle this could reveal the valve..there will be a clip with a tang pointing up.. Pull this clip up and pull the middle valve at once out..seem and notice if there is any undertaking caught interior the valve this could be a stable time to replace the valve..placing up is opposite..

Answer 6

yes in the northern hemisphere it turns clockwise because if you look at the earth fron the north pole it rotates anticlockwise

in the southern hemisphere water rotates anticlockwise because if you look at the earth from the south pole point of view it seems to rotate clockwise.

just like when your car turns left you fall to the right

Answer 7

It's true, weather patterns turn the opposite way to. Its because of the earths rotation.