If water comes into a leaky bathtub at a constant rate[br]and leaks out a a rate proportional to the height of the[br]water in the tub, then an equilibrium depth of water in the tub [br]can be reached.[br][br]This applet can be used to explore how the equilibrium depth depends[br]on the rate of flow into and the rate of flow out of the tub.[br][br]Clearly, the leaky bathtub is a metaphor for many equilibrium situations[br]that arise because of competing rates. A height of a helium balloon to which is tied a very long string is another example. Why? Can you think of other examples?[br][br]The applet chooses a random initial volume of water. You can then watch an animation by clicking on the "play" icon in the lower left hand corner of either window.[br][br][color=#ff0000][i][b]What questions could / would you pose to students based on this applet?[/b][/i][/color]