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Homework Help: Pascal's Principle on piston

  1. Jan 18, 2010 #1
    1. The problem statement, all variables and given/known data
    Imagine a hydraulically operated dentist's chair having a mass of 200kg, and in it is stiing a 54.8kg patient. The large piston below the chair has 5cm(diameter), while the small piston, moved by a pedal on which the dentist steps, has 1cm(diameter). What's the pressure in the interconnecting fluid when the dentist operates the chair? How much force must he exert on the small piston?

    2. A hydraulic lift consists of two interconnected pistons filed with a common working liquid. If the areas of the piston faces are 64cm^2 and 3200cm^2 and if 900kg car rests on the latter, how much force must be exerted to raise the vehicle very slowly?
    If the car is to be raised 2m, how far must the input piston be depressed?

    2. Relevant equations
    F/F2 =A/A2
    PA= F
    3. The attempt at a solution
    The answers for 1 are 1.27 x10^6 Pa and 100N...
    Answers for 2 are 177N and 100m.

    Please help.:(! I have no idea how to get these answers :((
  2. jcsd
  3. Jan 18, 2010 #2


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    Homework Helper

    P= F/A
    Find the total weight on the larger piston. Then find the pressure using the relevant equation.
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