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Homework Help: Find acceleration vector

  1. Oct 3, 2011 #1
    For the following position vector I am being asked to find the acceleration at t=1:
    r(t) = (t^5)i + 8ln(1/(6+t))j + (9/t)k

    I had the following for the velocity vector:
    v(t) = (5t^4)i + (-8/(6+t))j - (9/t^2)k

    For the acceleration vector I had:
    a(t) = (20t^3)i + (8/(t+6)^2)j + (18/t^3)k

    a(1) = 20 i + (8/49)j + 18 k

    According to the book, a(1) = 20i + 8j + 18k is the correct answer, does anyone see where I went wrong or is it a mistake in the book?
  2. jcsd
  3. Oct 3, 2011 #2


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    The book's wrong.
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