1. The problem statement, all variables and given/known data Hey folks, here is a question: A thread of mercury of lenght 15cm is used to trap some air in a capillary tube with uniform cross-sectional area and closed at one end. With the tube vertical and the open end uppermost, the lenght of the trapped air collumn is 20cm. Calculate the lenght of the air column when the tube is held. (i) Horizontally, (ii) Vertically with the open end underneath. (Atmospheric pressure= 76cm of mercury) In this question, am intrested in knowing what will happen when the tube is held horizontal and vertical as it will help in the calculation. What do they mean or it imply by refering the tube as having "uniform cross-sectional area"? Thank you as reply. 2. Relevant equations I know that this relates to boyle's law equation. P1V1=P2V2 3. The attempt at a solution V2= P1V1/P P1=15cm i.e lenght of mecury because lenght is directly propotional to pressure. I cannot go further because I don't know how to get my P1 and P2 respectively in case (i) (ii).