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Homework Help: Finding Instantaneous Velocity

  1. Jan 27, 2010 #1
    The position versus time for a certain object moving along the x-axis is shown. The object’s initial position is −2 m. Find the instantaneous velocity at 1s.
    http://img23.imageshack.us/img23/5285/phy1w.jpg [Broken]

    Using points (0,-2) and (2,7) I found the equation of the line to be =7/2x-2. Since this is a straight line I thought the tangent line would have the same slope. So, at 1s the instantaneous velocity would be 7/2, but this is not the correct answer. Where am I going wrong?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jan 27, 2010 #2


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    Slope of the line = (y2 - y1)/(x2 - x1).
    From 0 to 2 seconds this will be the velocity of the particle.
  4. Jan 27, 2010 #3
    Thanks for pointing out my now obvious mistake! I didn't even think to check to see if I had gotten the slope correct, I just assumed my understanding of instantaneous velocity was wrong.
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