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Homework Help: Finding partial solution

  1. Mar 8, 2010 #1
    Given that v= 20√10∙ ((1+Ae^(t/√10) ÷ (1-Ae^(t/√10) find the particular solution to satisfy the initial condition v(0) = 0.


    From my working I have come to the answer A = -1, is this correct? If not where could I be going wrong.



    My Working

    0 = 20√10 ∙ ((1 + A) ÷ (1 - A))
    0 = 20√10 ∙ (1 + A)
    0 = 20√10 + 20√10 A
    - 20√10 = 20√10 A
    A = -1
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: Mar 8, 2010
  2. jcsd
  3. Mar 8, 2010 #2

    HallsofIvy

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    Science Advisor

    Yes, that is correct.



    My Working

    0 = 20√10 ∙ ((1 + A) ÷ (1 - A))
    0 = 20√10 ∙ (1 + A)[/quote]
    It is simpler to divide by [itex]20\sqrt{10}[/math] and get 0= 1+ A immediately

     
  4. Mar 8, 2010 #3
    Thanks and yes I see the easier method of finding A now , oooops!

    The question goes on to say:
    You now have a solution for velocity, substituting this into y' = v. Use this to fing y(t) assuming that y(0) = 4000.

    Heres what I know.

    v= 20√10∙ ((1+Ae^(t/√10) ÷ (1-Ae^(t/√10)
    y= -1/2 gt^2 + At + B
    B = 4000

    Where do I go from here? Simply subs A = -1 y= -1/2 gt^2 + At + B
    and solve from there?
     
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