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Homework Help: Chair leg pressure problem geez

  1. Dec 3, 2006 #1
    Chair leg pressure problem....geez

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

    A 63kg person sitting on 3.5kg chair. Four legs contact the floor, each leg with circle 1.2cm in diameter. Find pressure exerted on floor by each leg of chair (weight evenly distributed).


    2. Relevant equations

    [{(person mass) + (chair mass)} * (9.81)] / pi (radius contact circle in meters)(4 chair legs)

    3. The attempt at a solution

    63kg + 3.5kg = 66.5kg total

    1.2cm diameter = 0.6cm radius = 0.006m radius

    area = 0.00011304 m^2 each leg
    area total four chair legs = 0.00045216 m^2

    P = F/A

    {(66.5)(9.81)} / 0.00045216 = 1442774.68 N/m^2

    ...thus for one leg = 360693.67 N/m^2

    answer of 3.6E5 and 3.61E5 incorrect.

    Answer unit requested is Pa.

    What am I missing here?
     
  2. jcsd
  3. Dec 4, 2006 #2

    Fermat

    User Avatar
    Homework Helper

    The pressure is the same for all four legs. You shouldn't have divided by 4.

    Pressure (on each/all chair leg(s)) = (total force) / (total area) = (partial force) / (partial area)
     
  4. Dec 5, 2006 #3
    Goofy err on my part. Actually had the answer correct the first time with 1442774.68 but posted my answer as 1.4E6....the correct way to post my answer was 1.44E6

    Thank you
     
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