Why does a pot start rotating when coffee is stirred inside? I usually make Turkish coffee as my morning coffee. I have a small somewhat rounded pot with handle on one side. I noticed that when I pour water in and start stirring, pot has a tendency to start rotating in the same direction as I'm stirring. 
Why is that?
 A: It is due to the viscous nature of any liquid. When you stir, the liquid starts spinning and this causes the liquid (the part which is in contact with the pot) to "drag" the pot(due to friction) along with it in the path of its motion.Hope this answers your question.
A: A probable explanation for this effect is simply that the bottom of the pot might be a bit bulged out, as to form only one point of contact around which the pot then can rotate relatively freely (with little friction).
As you stir the water inside the pot, the moving water molecules exert a frictional force on the walls of the pot, dragging it in the same direction as the water is moving.
For the same reason, the speed of a fluid inside a pipe is distributed in a quadratic manner, where the maximum speed is in the center of the pipe and the minimum speed at the boundary to the pipe itself. Frictional forces slow down the molecules closest to the stationary pipe.

A: You have made a model of a viscous fluid coupling which was used in a number of four wheel drive vehicles to transfer torque.  The system relies in the fact that adjacent planes of moving liquid experience a viscous force between them.
