 the
water started draining clockwise, then gradually slowed down and
finally started swirling in the opposite direction.?
?Do bathtubs drain counterclockwise in the Northern Hemisphere??
A more technical explanation can be found here.
?In a kitchen sink, of course, speeds and time scales are much smaller
than hours and miles. Water rushing down a drain flows at speeds on
the order of a meter per second in most sinks, which are themselves
less than a meter wide. Qualitatively, there doesn't seem to be much
chance for deflection. Quantitatively, putting these numbers into
Equation 1 results in an estimated change in rotation of only a
fraction of a degree per second, and a very small fraction at
that...less than an arc-second (1/3600th of a degree) per second over
the course of the entire draining of the sink, ignoring additional
effects caused by conservation of angular momentum and the like. Under
extremely controlled conditions, this can cause water to flow out of a
container counter-clockwise in the northern hemisphere and clockwise
in the southern hemisphere, but your kitchen sink is not so
controlled. Things like leftover spin from filling the sink (even when
the water looks still, it's rotating slowly for a long time after it
seems to stop), irregularities in the construction of the basin,
convection currents if the water is warmer or colder than the basin,
and so forth, can affect the direction water goes down the sink. Any
one of these factors is usually more than enough to overwhelm the
small contribution of the Coriolis effect in your kitchen sink or
bathtub. Research in the 1960s showed that if you do carefully
eliminate these factors, the Coriolis effect can be observed.?
"Getting Around The Coriolis Force"
Search terms used:
water drains clockwise rotation coriolis Shapiro
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