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Homework Help: How to calculate instantaneous acceleration?

  1. Feb 1, 2012 #1
    This is the graph and question:
    http://img193.imageshack.us/img193/3489/physicquestion.jpg [Broken]

    I cannot seem to find the instantaneous acceleration. I must be doing it wrong because I'm pretty sure to find the the inst. acceleration all i need to know is the tangent line equation.

    I've tried a bunch of answers but can't seem to get it right. I need to express the answer in m/s^2 and not km/h but that is easy to convert.

    I haven't had much physics experience. How do i find the instantaneous acceleration?

    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Feb 1, 2012 #2
    Since the acceleration is uniform, instantaneous acceleration = average acceleration.

    acceleration = slope of v-t graph

    from the graph, the slope of the graph during time = 30s to 40s is a straight line (that means the slope is not varying), that means the acceleration uniform.

    so the instantaneous acceleration at time = 35s :
    = [(60/3.6) - 0 / (30 - 40)] = -1.667 m/s^2.
    Last edited: Feb 1, 2012
  4. Feb 1, 2012 #3


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    That's correct, so what is the definition of instantaneous acceleration and what is the slope of that line at t = 35 s?
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