Friday, July 11, 2014

The direction of rotation of a draining sink is determined by the location on northern or southern hemisphere?

Before talking about the subject, let me introduce myself first.  I am from Taiwan and this is my first time to Boston.    I received my MBA degree from National Taiwan University and have worked in financial industry for 17 years.  I started a venture capital firm with my colleague 3 years ago.    Because I never had a chance to study abroad,  I always dreamed I could spend some time  as a student in USA.   Now my dream come true.  It is my honor to learn from Professor Berman  and get to make new friends!
About today's field trip to "Lady's restroom" to observe the direction of rotation of a draining sink,  there were quite many different observations from everyone in the class.  For my observation, I saw the direction is clockwise.  To make sure  it is right ,  I made 4 more experiments (one in my bath room sink , the other tree in kitchen sink)after I came home.  To my surprise, there are two clockwise  and two counterclockwise rotations.   I start to assume the direction of rotation of a draining sink is not determined by the location on earth but by another factors(e.g. size of sink, water level) .
To confirm my assumption,  I make some research on internet. The three sources I looked up all lead to same conclusion " The direction of a draining sink is determined by the way it is filled or by vortices introduced while washing".  The Coriolis Effect is too small to be relevant when you pull the plug of the sink!
Source:
1.http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html
2.http://math.ucr.edu/home/baez/physics/General/bathtub.html
3.http://www.loc.gov/rr/scitech/mysteries/coriolis.html

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