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Homework Help: Piston Conundrum

  1. Mar 6, 2013 #1
    1. The problem statement, all variables and given/known data

    In the picture below, the pressure on either side of the piston is equivalent. The question asks which direction the piston moves (or if it even moves at all).

    http://imageshack.us/a/img203/1830/photoon3613at919pm.jpg [Broken]

    2. Relevant equations

    P1*V1 = P2*V2 = C

    P = F*A

    3. The attempt at a solution

    Moving the piston to the left decreases volume in the cylinder, and moving the piston to the right increases the volume in the cylinder, but I see no reason for the piston to move if the pressure on both sides is equal. Also, the force on the right side of the piston is less than that on the left side, making the force greater on the right side if we use the equation P = F*A and pressure is equal on both sides. At first glance it just looks like it will not move, but I feel like I am underthinking it.
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Mar 7, 2013 #2


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    What is that in the left end of the tube?

  4. Mar 7, 2013 #3

    rude man

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    Gold Member

    Probably a stopper.
  5. Mar 7, 2013 #4


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    Well, that depends. What is the pressure on the outside of the entire apparatus? More specifically, how does the pressure on the outside of the apparatus compare to the pressure inside? That plays a role, given that the shaft is sticking out.


    Oh, and by the way,
    I think you mean F = PA.
    Last edited: Mar 7, 2013
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