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Homework Help: Why can't I substitute a Laplace transform into an integration?

  1. May 22, 2012 #1
    Hi, I was given the attached question and have given my wrong attempt at the answer. I know how to work the answer out (also shown) but I would like to know why my first attempt is wrong.

    Many Thanks

    Attached Files:

  2. jcsd
  3. May 22, 2012 #2


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    First, you calculated u'(t) incorrectly. Second, when you said v=2/s2, you used the definite integral of dv/dt. You need to use the indefinite integral. You can't get rid of the t dependence.
  4. May 22, 2012 #3
    Yup, I integrated it by mistake. That now makes it equal zero incidentally.

    Awesome, Thanks for for that. Makes sense now.
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