Atmospheric pressure and weight measurement

[cyriac]

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

 

[Bystander]

"Why 100kPa?" That is what is measured.

 

[willem2]

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.

 

[cyriac]

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

 

[Chestermiller]

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.