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Atmospheric pressure and weight measurement

  1. Dec 29, 2015 #1
    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
  2. jcsd
  3. Dec 29, 2015 #2


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    "Why 100kPa?" That is what is measured.
  4. Dec 29, 2015 #3
    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.
  5. Jan 4, 2016 #4
    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
  6. Jan 4, 2016 #5
    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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