Question

Why the level of mercury falls as altitude increases
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Answer 1

Answer:

As the atmospheric pressure rises or falls so the mercury level in the tube rises or falls. ... Up a mountain the air pressure is low and so the barometer reading will go down. Any air above the mercury in the tube will actually push the mercury down so giving a low reading for the atmospheric pressure.

Answer 2

• Air is a gas.

• Gases and liquids are fluids.

• They both have weight when put in a gravitation field.

• So, in the same way, the pressure in the sea rises with depth so does the atmospheric pressure rise when you go to a lower position.

• The difference is that liquids being practically non-compressible, the change of pressure with depth is linear in liquids, while, not only the pressure but also the change of pressure with altitude is a function of the altitude in the atmosphere.