volume_mute
Pressure equality in a barometer
publish date: 2026/05/19 19:27:56.338302 UTC
volume_mute
It is stated that 'the pressure at point A must equal the pressure at point B because the points are at the same level.' In a mercury barometer, pressure at point A (inside the tube at the level of the mercury pool) equals what?
Correct Answer
Atmospheric pressure outside the tube at the same level
Explanation
In a fluid at rest, pressure at the same horizontal level is equal. Point A (inside the tube at the pool level) and point B (outside the tube at the pool surface) are at the same level. The pressure at B is atmospheric pressure, so the pressure at A must also equal atmospheric pressure. This pressure at A is caused by the weight of the mercury column above it.
Reference
Basic Physics: A Self-Teaching Guide