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Finding Velocity on a Position/Time Graph

  1. Oct 8, 2012 #1
    Hey everyone, i'm having trouble finding velocity on a straight line position/time graph. Every single equation I do ends up with a different answer, which doesn't make sense because it's a straight line.

    I know the equation is

    Vf-Vi/Tf-ti

    The answer to this question is 1.4m/s N

    Example:

    45-25/28-16= 1.666666m/s Wrong answer. I'm just taking these from the graph by the way.

    25-20/16-14= 2.5, completely different answer.

    Could someone please explain what i'm doing wrong? I'm calculating the slope which seems to change with every calculation that I do, which I understand is wrong.
     
  2. jcsd
  3. Oct 8, 2012 #2
    Try to post the graph so we can see it. Also, if your v is velocity, you are dividing a velocity change by an elapsed time. That gives acceleration. If you want velocity, divide displacement by time.
     
  4. Oct 8, 2012 #3

    SammyS

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    Hello 5pirit. Welcome to PF !

    What is the slope of that line?
     
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