Saturday, July 12, 2014

Catherine Zhang --Assigment 1: which way the water drains in the sink?

          I am Catherine Zhang from China, I love animals and all things related to them. I always want to go to science field trips, but since my parents have huge exception of business major from me, I always focus on the classes required to take. After struggling to consider which class I will choose in the next four weeks, I will stick with this fun class to the end. Because I like the subject and I finally can try something I love since high school.

          This field trip is to observe which way (clockwise or counter-clockwise) the water in the school bathroom sink drains. The location of the field trip is in the female restroom on the basement of the Metropolitan College. To see how the sink water drains, my classmate used one hand to cover the drain to keep water. As he removed his hand, the water drains and small water waves showed up which is either clockwise or counter-clockwise.

          What I did is to observe two sinks in the restroom and water in them. I think he water in my team showed the direction of clock-wise. But when I saw the other sink, I observed that it seemed water drained of the direction of counter clock-wise. Again when I got back to the previous sink and tried it again, the water still stained as clock-wise. When I got back home, I also tried the sink of my apartment,  it showed the water drained clock-wise. So my hypothesis is that water in the Northern Hemisphere drains clockwise, but the water in the Southern Hemisphere drains counter-clockwise.

          I first used my own language to search "Does the water flow the opposite direction in Northern and Southern Hemisphere?" It gives me one thing: Coriolis force. It says the rotation of the draining water relates with it, and Coriolis force is the result of Earth rotation. On University of Illinois’ web page, a direct image shows how Coriolis force works. (Coriolis Force: an artifact of the earth's rotation). So on the Northern Hemisphere, the water drains counter-clockwise and clockwise on the southern Hemisphere. In the article “Does Water Drain in Different Directions in Northern, Southern Hemispheres? (VIDEO)”, the Doctor Paul Doherty used an experiment to show on the Northern Hemisphere, the water does drain counter-clockwise.

          What I like the most is a video I found on Youtube( Video “SchoolFreeware Science Video 11 - Science Down The Drain - Is The Rotation From The Coriolis Force?”). In the video, the speaker first declared that he is on the Northern Hemisphere, he also explained the Coriolis force , and then he did the same draining water experiment in several sinks with different directions of faucet which the water can come out in the middle, on the left and on the right. As the faucet was in the middle, the water drained counter-clockwise as he used ink to show water direction. But as he pulled water from the left side of the sink, the water drained counter-clockwise; he then did the same experiment with faucet on the right side as water came out. This time the water drained clockwise. I think it is because that as the speaker let water drain as soon as he fill the sink, at that time the water was still moving the direction as the water was filling the sink. If the water is steady, the result will be the same as the one with water coming out from the middle. Now I know  I also flushed the toilet, with fast moving water; I finally can tell that the water did drain counter-clockwise. 

PS: It reminds me that in the movie “Escape Plan” (It is about two people tried to find a way out in the world’s most secure prison, Arnold Schwarzenegger and Sylvester Stallone are both in it), sylvester Stallone found out he was on the Northern Hemisphere from the drain direction of toilet water. It is an awesome movie with two tough old men!

Coriolis Force: an artifact of the earth's rotation :

Does Water Drain In Different Directions In Northern, Southern Hemispheres? (VIDEO) :

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