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I know due to atmospheric pressure the weight of an object increases, but when we take measurements we do not omit the weight of the column of air above it. So, doesn't it affect the accuracy of our calculations?

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I know due to atmospheric pressure the weight of an object increases, but when we take measurements we do not omit the weight of the column of air above it.

No, it is actually the other way round.

The weight of an object decreases due to the buoyant force from the displaced air. According to Archimedes' principle the buoyant force is equal to the weight of the displaced air. The buoyant force points upward because the air pressure is larger at the bottom of the object than at the top of the object.

The density of air is around $1.2$ gram/liter. So the difference is actually not difficult to measure, for example by weighing a solid container filled with air, and comparing it to the same container emptied by a vacuum pump.

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  • $\begingroup$ what if there is no air below ? $\endgroup$
    – Ankit
    Dec 23, 2020 at 15:40
  • $\begingroup$ Additional information: Derek Muller (youtube channel: Veritasium) has a video titled The largest weight. He visits an institute where (among many other things) force transducers are calibrated. The biggest weight in that institute is a million pounds. That much metal displaces so much air mass that they have to take that into account. On a given day the air density on that day is used in the calculation, so that the correct air buoyancy correction is applied. $\endgroup$
    – Cleonis
    Dec 23, 2020 at 16:23

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