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Homework Help: Hydraulic Lift piston

  1. Oct 5, 2008 #1


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    1. The problem statement, all variables and given/known data
    The 70kg student in the figure balances a 1200kg elephant on a hydraulic lift. A second 70kg student joins the first student. How high do they lift the elephant?
    diameter of the piston elephant is on = 2.0m
    diameter of the piston student is on = 0.48m
    The liquid inside the lift is oil, therefore rho = 900 kg/m3
    Out would be elephant, In would be the students

    2. Relevant equations
    Fout/Fin = Aout/Ain
    Fout=Aout/Ain x Fin - [tex]\rho[/tex]ghAout

    3. The attempt at a solution
    I tried both equations
    Fout/Fin = Aout/Ain
    (rho x g x h x Aout) / (140 x 9.8) = (pi x 12) / (pi x 0.242)
    which ended giving me h = 0.86m which was wrong.

    When i tried it with the other equation i ended up with 0.44m which was wrong as well.

    I am not sure if I'm using the wrong formula though so someone please give me some guidance.
  2. jcsd
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