text: yes, it will move.  the phenomenon responsible is known as the bernoulli effect,  and its most basic statement is that "in a flowing fluid, an increase in flow rate causes a decrease in pressure".  what you have constructed is essentially a kind of venturi tube, which is often used to illustrate the bernoulli effect.  here is a great page about venturis and the bernoulli effect:\nhttp://home.earthlink.net/~mmc1919/venturi.html\n\nso anyway, when you stir the water in the glass, it moves faster.  if the orifice is underneath a region of quickly-moving water, the pressure above the orifice will be decreased.  this will cause the ball in the tube to move towards the lower-pressure area (that is, the glass you stir).  \n\nif the orifice is in the center of the glass, then the water will not be moving very quickly, and the pressure will be higher there.  towards the outer edge of the glass, the water will be moving fast, so this will cause a relative decrease in the hydrodynamic pressure.  so, i would reason that the closer the orifice is to the edge of the glass, the greater the movement of the ball.