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Homework Help: What is the net force on the roof

  1. Dec 5, 2008 #1
    1. The problem statement, all variables and given/known data
    If wind blows at 35 m/s over a house, what is the net force on the roof if its area is 240 m2 and is flat?



    2. Relevant equations

    Pat + 1/2 * pair * v^2

    3. The attempt at a solution
    wind velocity - v - 35
    area of roof - A - 240
    density of air - p - 1.29
    atmospheric pressure - Pat - 100,000

    Fnet=?

    P = total pressure = Pat + 1/2 * p * v^2
    Fnet = P * A = 24,200,000 N

    but answer provided was 1.9 * 10^5 N
     
  2. jcsd
  3. Dec 5, 2008 #2

    LowlyPion

    User Avatar
    Homework Helper

    Aren't you just interested in the dynamic pressure term across the area of the roof?

    1/2 * 1.29 * 352 * 240 = ...
     
  4. Dec 5, 2008 #3
    yes i am :)
     
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