A 10 cm long gas column is trapped by a 4 cm long column of mercury in a capillary tube, as shown below, when the tube is held horizontally in a room at an external pressure of 1 atm. The length of the air column when the tube is held vertically with the open end up is
9.5 cm
Since temperature is constant; when the tube is horizontal:
P1 = 760 mm V1 = 10A (A=area of cross section)
When the tube is vertical :
P2 = 760 +4 = 764 mm V2 = ?
P1V1=P2V2
760×10A=764×V2 V2 = 9.5A
∴ length of air column = 9.5 cm (as area of cross section is the same).