The figure shows a simple barometer which consists of a U-tube with one end closed (1) and the other end open to the atmosphere (2).
The liquid in the barometer is mercury, with a density of ρHg = 13.6 g/cm3. The height of mercury in column 1 is h1, and the cross-sectional area is A1. The height of mercury in column 2 is h2, and the cross-sectional area is A2. Volume 1 is filled with an unknown gas.
What is the best expression for the pressure in volume 1?