A Digital Potter's Pitchers - I

The right hand panel shows a cross section of a vessel made by a potter whose style is to make vessels in the forms of conical frustrums stacked on top of one another. The potter wants to know the volume of the vessels she makes. [all the vessels have rotational symmetry about the vertical line.] You can shape the vessels by dragging the BLUE dots and the GREEN dots in the right hand panel. When you click on the restart button in the left hand panel the vessel will fill and a volume vs. height graph will be traced out. What questions could / would you put to your students based on this applet?