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Homework Help: Need some help with a area question

  1. Jun 17, 2007 #1
    1. The problem statement, all variables and given/known data

    The force (in Newtons) that air exerts on a surface is given by the formula
    F = 10^5A

    Where A is the surface area (in square metres). Suppose that the air supplies 10^6 Newtons of force on a rectangular surface that is 2 metres longer than it is wide. Find the dimensions (to 2 decimal place) of the rectangular surface.

    2. Relevant equations



    3. The attempt at a solution

    This is my attempt

    10^6 = 10^5A
    A= 10

    10 = LW
    10 = (2+w)w
    10= 2w +w^2

    now i am stuck here..

    If anyone knows what to do it would be greatly appreciated if you could help me out, thank you.
     
  2. jcsd
  3. Jun 17, 2007 #2

    danago

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    Gold Member

    Its a quadratic. Could use the quadratic formula
     
  4. Jun 17, 2007 #3
    so what i did was corrent, i just gotta use the quadradic formula and thats it yeh?
     
  5. Jun 18, 2007 #4

    danago

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    Gold Member

    As far as im aware, yes.

    For a quadratic like that, the first thing i would do is write it as:

    w2+2w-10=0

    And see if i can write it in the form (x+a)(x+b)=0. If not, then id probably proceed to use the quadratic formula.
     
  6. Jun 19, 2007 #5

    HallsofIvy

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    Science Advisor

    Starting from w2+ 2w= 10, completing the square leaps to mind!
     
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