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Gauge pressure and atmospheric pressure

  1. Oct 29, 2015 #1
    1. The problem statement, all variables and given/known data
    Objects A and B are submerged at depth of 1m in a liquid with specific gravity of 0.877. Given that density of object B is one third that of object A and that the gauge pressure of object A is 3atm, what is the gauge pressure of object B? (assume atmos pres is 1 atm and that g = 9.8m/s^2

    2. Relevant equations
    p_gauge = P - P_atm

    3. The attempt at a solution

    I think I do understand gauge pressure, that it is a difference in pressures. Specifically the diff between atmospheric pressure and the pressure in the container. But I think of gauge pressure always in terms of a tire. Thats whats confusing me. Is the question saying that the objects have enclosed air that is at a certain pressure? I have the answer but failing to put the concepts together, please help thanks
  2. jcsd
  3. Oct 29, 2015 #2


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    Gauge pressure normally means that when the pressure gauge reads zero, there is still atmospheric pressure present. Absolute pressure, on the other hand, means that the pressure scale reads zero when there is a perfect vacuum present. Atmospheric pressure has a non-zero reading, like 14.7 psi or 101.325 kPa, on the absolute pressure scale.

    Still, given the particulars of the problem statement, since the two objects are submerged to the same depth in the same liquid, what does this tell you about the pressure of object B, given the pressure of object A?
  4. Oct 29, 2015 #3


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    The wording is indeed strange. Since you know nothing else about the objects, it is curious to speak of the gauge pressure of the objects. Surely it means the gauge pressure on, or at, the objects?
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