Physics Help Forum Determining absolute pressure

 Jul 22nd 2009, 12:44 PM #1 Junior Member   Join Date: Jul 2009 Posts: 13 Determining absolute pressure Hi all. I have a question but I think the question is not worded very well from the author. Question. A large chamber is seperated into compartments 1 and 2, the chambers have seperate different value pressures inside. Each chamber has a pressure gauge attached. Chamber 1 gauge reads 400 Kpa, and chamber 2 gauge reads 180Kpa. These pressures are "Gauge Pressure". If a barometer reads 720 mmHg, determine the absolute pressure reading Gauge 3. Thoughts My confusion with the question really is to do with the two chambers, which I read to understand that they are "seperate", which to me I understand as "Independent" of each other? I am then give four possible answers to the problem. A = 320 Kpa B = 300 Kpa C = 280 Kpa D = 260 Pka I am thinking that I should be solving the problem this way; Chamber 1 is independent of chamber 2, therefore changing any value of pressure in chamber 2 should have no effect on chamber 1, which means that chamber 2 at 180 Kpa + 100 Kpa atm approx would show on gauge 3 as a result of; C = 280 Kpa. The solution given by the author shows; 400 - 180 = 220 + 100 = A = 320 Kpa My confusion If the authors solution to this problem is correct, how does a subtraction of an independent pressure of 180 Kpa from 400 Kpa have an effect on the gauge reading 3. Surely to my mind if the chambers are independent and pressures are different he must have made a mistake? Any help or advice appreciated
 Jul 29th 2009, 05:07 PM #2 Junior Member   Join Date: Jun 2009 Posts: 24 Atmospheric pressure of 720 mmHg corresponds to 96 kPa.
Jul 31st 2009, 02:45 PM   #3
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 Originally Posted by george Atmospheric pressure of 720 mmHg corresponds to 96 kPa.
Thank you for your input George, however, the question is asking for something else?

David

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### pressure in a chamber is 300 mm hg . the absolute peessure is

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