Atmospheric pressure and weight measurement

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Atmospheric pressure is defined as 100 kPa, which equates to a force of 100,000 N per square meter, but this does not directly translate to an additional weight on scales. The confusion arises from the fact that while atmospheric pressure acts on all surfaces, it is balanced by the forces acting on the scale itself. When a person stands on a digital scale, it measures only their body weight, not the additional weight of the air column above. The scale accounts for atmospheric pressure in its design, ensuring that the net pressure forces are zero. Therefore, the scale reflects only the weight of the individual, not the combined weight of the atmosphere.
cyriac
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Whats the significance of Atmospheric pressure being refereed as 100kPa ? Does that really mean 10000 kg/m2 acting upon us ?

If we are measuring only collision force on the surface and not the weight of the entire column of air above us, then why figure 100kPa (100000 N force/m2) which is huge and significantly more than what is required to raise mercury level by just 76 cm
 
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"Why 100kPa?" That is what is measured.
 
cyriac said:
why figure 100kPa (100000 N force/m2) which is huge and significantly more than what is required to raise mercury level by just 76 cm
The density of mercury is 13.54 g/(cm^3), so a square meter of mercury with 76 cm thickness weighs 10300 kg, and would need a force of 101000N to lift it up.
 
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Thanks for replying
Then why a digital weighing scale doesn't pick that force. When we stand shouldn't it pick up 80kg + 10000kg ?
Or is the scale being adjusted only to reflect body weight
 
cyriac said:
Hi
Thanks for replying
Then why a digital weighing scale doesn't pick that force. When we stand shouldn't it pick up 80kg + 10000kg ?
Or is the scale being adjusted only to reflect body weight
The scale doesn't have to be "adjusted." The pressure acts on all parts of the scale, including parts facing downward (which receive an upward force from below). The net pressure forces on the scale are zero.
 
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