The Fun of Three Bottles
Pressure of atmosphere is all pervading in our surrounding. Also it shows up in various ways. Liquid columns have their own pressure. While atmospheric pressure is almost uniform over heights of tens of meters, liquid pressure varies significantly with depth of the column. We are giving a fun-filled way to understand and practice these phenomena.
Three bottles give enough room for discussion of air and water pressure. Flow direction in a tube is decided by the pressure difference at the two ends. Calculation of pressure at end of the tube involves air expansion or contraction if the cap is closed and any water column above that end.