When I stir my tea with a spoon, I observe that the tea leaves all eventually concentrate in the center of the cup. Clearly they go against the centrifugal force. Why?
Yet when I put the cup in the center of the rotating platter of my gramophone turntable, the tea leaves concentrate at the edge following the centrifugal force.
The surface of the tea is concave with the depth lower in the center in both cases. Thus the pressure in the center cannot be higher than at the edge. The tea leaves drown, so they are heavier than water and should not move to where pressure is lower.
So why do the tea leaves move to the center?
In response to the possible duplicate, the earlier question does not include the case of a rotating turntable and therefore has a lesser scope. In addition, the method of stiring is different, so the question is not a duplicate. Finally, the earlier question does not have a complete correct answer, but only a reference to the Elkman layer for a further research. Thus my question is not at all addressed earlier from any angle. The second link also does not address the case of the rotating turntable, explaining where, how, and why the leaves would collect in this case.
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