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Homework Help: Displacement and 1-D Kinematics

  1. Sep 8, 2009 #1
    [SOLVED] Displacement and 1-D Kinematics

    1. The problem statement, all variables and given/known data
    A runner runs 15 km, in a straight line, in 20 min and then takes 45 min to walk back to the beginning. Find the average velocity for the whole trip.

    2. Relevant equations
    Vav= (Xf-Xi) / (tf-ti)

    3. The attempt at a solution
    Wouldn't the displacement be 0? If so; what is the average velocity of the whole trip? It couldn't be 0.

    It would be 0. Silly me.
    Last edited: Sep 8, 2009
  2. jcsd
  3. Sep 8, 2009 #2
    Re: [SOLVED] Displacement and 1-D Kinematics

    Where is this equation from?

    Tackle the problem from two parts: find the speed of his run, and the speed of his walk, and average them.

    You know S = d/t yes? So convert the time to hours, do the question in two steps and average.
  4. Sep 8, 2009 #3
    Re: [SOLVED] Displacement and 1-D Kinematics

    Yup; thanks. I figured it out.
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