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Homework Help: Energy problems/work check

  1. Dec 16, 2006 #1
    can someone check my work please thanks, oh btw Im still trying to learn how to use LaTeX mathematical typesetting; I figured itll be slightly faster taking a picture of the problem and my work and posting it here so please bare with me :redface:

    1. The position of a toy locamotive moving on a straight track along the x-axis is given by the equation x = t^3 - 6t^2 + 9t, where x is in meters and t is in seconds. The net force on the locomotive is equal to 0 when t is equal to (a) zero (b) 2s (c) 3s (d) 4s (e) 5s

    (my work)
    x = t^3 - 6t^2 + 9t
    v = 3t^2 - 12t -- first derivative
    a = 6t - 12 -- second derivative
    0 = 6t - 12
    12 = 6t
    t = 2s

    Question 2: http://ourworld.cs.com/LezardV4leth/problem_2.jpg [Broken]
    Work: http://ourworld.cs.com/LezardV4leth/problem_2_work.jpg [Broken]

    Question 3: http://ourworld.cs.com/LezardV4leth/problem_3.jpg [Broken]
    Work: http://ourworld.cs.com/LezardV4leth/problem_3_work.jpg [Broken]
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Dec 17, 2006 #2


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    Gold Member

    Looks ok to me...

    BTW, don't count too much on us to systematically check your homework :smile:
    We want to help with specific difficulties, misunderstandings or so, but we're not here to do the algebra checks for you :wink:
  4. Dec 17, 2006 #3
    oh haha ^^;; Ill make note of that next time thanks alot though
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