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Atmospheric pressure effect on simple mechanisms

  1. Jan 27, 2013 #1
    Please see attachment. Will be happy to receive comments/responses on the doubts raised.

    Attached Files:

  2. jcsd
  3. Jan 27, 2013 #2


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    If both sides are in contact to each other, expansion of both sides should be the same independent of air pressure - you have the same net force of F1 acting on both. With air pressure, you just need a stronger attracting force to reach that situation (assuming vacuum in the boxes).
  4. Jan 27, 2013 #3
    Thanks. case1: Both parts are in contact at F1 at say P1 all round atmospheric pressure.
    Case 2 : Keep increasing atmospheric pressue in such a configuration. I look at what happens as follows; Let us just look at the diaphragm alone. Though in contact, it will fee the effect of increasing atmosphric pressure and pass it on to loadcell since this is in contact with it. It is sometibng like 2 people hugging each other and increasing the pressure of hugging. They will both experience increasing pressure on each other as the hugging pressure keeps increasing. Movemnt may not happen till each other's body provides the necessary reaction .At a certain point, the weaker person is likely to crack apart yeielding eventually to the pressure. In a situation like this , we should see what happens to one of the persons. He will experience both 'pull' pressure and 'push' pressure. Hewill receive and provide reaction and remain in the same locatin for some time possibly manifesting in an efffect that makes it appear that he experiences a force F1 only. But if reaction given is less than reaction received as an example, under increasing atmospheric pressures, one side will yield more easily and there could be net displacment. I think this requires serious thought and another review please. Thanks once again. Look forward to further esposne based on these points.

    Best regards,

  5. Jan 28, 2013 #4


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    Air pressure tries to pull them apart, I think. This assumes that the contact area is not very smooth or even wet, which would give interesting new effects.
    The forces at the contact area are perfectly symmetric in equilibrium.

    Oh, and you might get some sort of hysteresis effect: You need current I in the electromagnet to establish contact, but you can keep contact with a current I'<I as the magnets are closer to each other.
  6. Jan 30, 2013 #5
    I like to change the question for easier communication of the probelm issue and better clarity.
    1.Two people are pushing each other body to body not hugging !
    2. If the force appllied by both is same , no net movement results eventhough both will feel the force exeted by the other person.
    3.Both people keep on increasing this 'push' force progressively and imagine that both are not made of the same build or strength.
    4.At some point , the weaker person is likely to be moved by the push force applied by the strong person.
    5.Imagine at start point of discussion both these persons are applying a steady push force of F1 at a very low atmospheric pressure zone of say 3000 meters above sea level and no net movement results now.
    6. Withouy any change in this force f1 that each exerts on the other they are moved progressively down to sea level from 3000 meters height.
    7. I would expect that weker person will theoritically be moved by the stronger person's push force as stated in point 4 above!(Only tendency being dicussed without exact equations or addressive real quantitative issues!

    Inviting comments!

  7. Jan 30, 2013 #6


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    No net acceleration. If the initial state has no movement, it will stay that way.

    If they cannot support the same force with their feet or any other part of their body, right.

    In this example, air pressure is irrelevant - it acts on both bodies in both directions, and cancels completely.
  8. Feb 4, 2013 #7
    If they cannot support the same force with their feet or any other part of their body, right...

    In respect of the above, I would say, yes, the situation is that as the push force keeps on increasing from one person , the other weak person too needs to keep on increasing his reaction force to stay in same place. A point in reached in this process when the weak person is just short of his capacity to apply the reaction force to balance the force applied by the stronger person.

    Now both bodies are in contact. consider the weaker person. At this point, if atmospheric pressure keeps on iincreasing multiple fold, he will experience an increaing but equal force on the front and back of his body frame and he has to provide reaction in both sides to keep balancing the incresing atmospheric pressure. If he is not able to do this under increasing atmospheric pressure , he may be crushed. For the sake of arguement , if his ability to apply reaction on two opposing directions to balance the increasing atmosphric proessure is not equal, then he may start crashing from one side.

    I dont know if I am right, consused or confusing.

    Thanks a lot mfb, though your write up has made me to think further, I feel still what I have written above is the situation. your further remarks/clarifications may prove useful for my better understaning. Once again, many thanks and best regards,

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