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Homework Help: Hydraulic lift/Pressure

  1. Nov 4, 2007 #1
    1. The problem statement, all variables and given/known data
    Piston 1 in Figure P9.24 has a diameter of 0.32 in.; Piston 2 has a diameter of 2.0 in. In the absence of friction, determine the force, , necessary to support the 500 lb weight.

    Picture
    http://www.webassign.net/sf/p9_24.gif

    2. Relevant equations

    F1=(A1/A2)F2
    A=pi*r^2

    3. The attempt at a solution
    I solved for F1 using the above equation and got 12.8. THIS IS WRONG Is this because the column of fluid is higher in the larger piston? So i have to factor in the weight of the higher water as well? Can someone please point me in the correct direction?

    thanks
     
  2. jcsd
  3. Nov 5, 2007 #2

    learningphysics

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    you got the force that the piston at 1 exerts upwards... what force does the hand need to exert to keep the piston from moving.. use torque.
     
  4. Nov 5, 2007 #3
    torque=rF

    would the radius be from the hand to the center of piston 1?
     
  5. Nov 5, 2007 #4

    learningphysics

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    Homework Helper

    you want the torque about the point next to the piston 2. so torque due to the F force is F*12.0in clockwise... what is the torque due to the pressure force...
     
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