Force necessary to support mass on Hydraulic Jack?

  1. Force necessary to support mass on Hydraulic Jack???

    1. The problem statement, all variables and given/known data
    Piston 1 in the figure has a diameter of 1.31 cm. distance of 2 in
    Piston 2 has a diameter of 7.91 cm. distance of 10 in
    In the absence of friction, determine the force F, necessary to support an object with a mass of 904 kg placed on piston 2. (Neglect the height difference between the bottom of the two pistons, and assume that the pistons are massless).

    2. Relevant equations
    F1*d1 = Fp*d2, where d1 is the moment arm of F1, and d2 is
    the moment arm of Fp.

    3. The attempt at a solution
    Fp = (F1*d1)/d2
    (904)(9.81)/(pi)(0.003955)^2= F/(pi)(0.00655)^2
    F=242.98 N which was incorrect.
    anyone have an idea of what I should do and what equation to use? Thanks!
     
  2. jcsd
  3. Redbelly98

    Redbelly98 12,036
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Force necessary to support mass on Hydraulic Jack???

    I think we'll need to see the figure before we can help you out.
     
  4. djeitnstine

    djeitnstine 619
    Gold Member

    Re: Force necessary to support mass on Hydraulic Jack???

    Neglecting the height difference means the pressure should be the same, thus [tex]F_1 A_1 = F_2 A_2 [/tex]

    This is would be the force exerted on the small piston.

    You should know how to find the force needed by the hand from this.
     
  5. Redbelly98

    Redbelly98 12,036
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Force necessary to support mass on Hydraulic Jack???

    You have correctly found F1, the force on the smaller piston. However, they are asking for Fp (labelled simply F in the figure), the force exerted by the hand.

    You have the equation to find Fp given F1.
     
  6. Re: Force necessary to support mass on Hydraulic Jack???

    ok. I used the equation given and solved for Fp. I had (242.98)(pi*(0.03955)^2))/(pi)*(0.00655)^2=Fp=8858.92 N, which is also incorrect.
    what am I doing wrong?
     
  7. Re: Force necessary to support mass on Hydraulic Jack???

    nvm. I solved it! thanks everyone for your input!
     
  8. Re: Force necessary to support mass on Hydraulic Jack???

    how u solved it my friend?
     
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