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Homework Help: Need help with Pistons

  1. Apr 10, 2010 #1
    1. The problem statement, all variables and given/known data

    Piston 1 in the figure has a diameter of 0.27 in and is attached to a lever arm a distance 1.8 in from the pivot point. Piston 2 has a diameter of 1.3 in. An external force F acts on the
    lever arm at a distance 20 in from piston 1 as shown below. In the absence of friction, find the force F necessary to support the 464 lb weight. Assume the height difference between the pistons is negligible.
    Answer in units of lb.

    2. Relevant equations

    Force
    in/Areain = Forceout/Areaout

    3. The attempt at a solution

    The picture is #1 on the attached files.
    I'm not even sure you're supposed to use this formula, but I have no clue how to solve it. Can someone please guide me in the right direction. Thanks

    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Apr 11, 2011 #2
    hi, I was trying to solve the problem with the bernoulli's equation on your other post, and saw that you said you need help with this one, and i happened to just solved it, so i thought i'll stop by, hope it's not too late for your quest thing...


    I did (A1/A2)*464lb
    so, [pi*(0.27/2)^2]/[pi*(1.3/2)^2] times 464lb = x

    then you have to do the mechanical ratio thing.. sooo

    (shorter distance/ (shorter distance + longer distance) ) times the above answer you just found = what you need

    [1.8/ (1.8+20)]*x = what you need

    and i'm still having problem with the bernoulli's equa :(
     
  4. Apr 11, 2011 #3
    and here's all the technical stuff:

    x i mentioned above is force of small piston produced... fyi

    technical stuff on the 2nd step:
    +F1d1 - Fd = 0
    +F1d1 = Fd
    so F = (d1/d)*F1
     
  5. Apr 11, 2011 #4
    and nvm i got the bernoulli's equ :)
     
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