Question

4. A mercury barometer reads 75 cm. Now 3 cm of
atmospheric air is introduced into the tube. The
mercury falls to a height of 65 cm and the length of
air column above the mercury is found to be 15 cm.
Calculate the cross-sectional area of the barometer
tube.
​

Answer 1

Answer:

Let the new pressure inside be P after air introduced.

For the air,

P1V1=P2V2

⟹P(50)=(75)(2)

⟹P=3 cm of Hg