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Help finding velocity using data table

  1. Jan 4, 2014 #1
    1. The problem statement, all variables and given/known data

    Using the data found, in this chart, create a time-velocity data table.

    Time(s),Position(m)[down]: (0,0), (0.25,0.29), (0.50,1.15)

    2. Relevant equations

    v= change in position/change in time

    3. The attempt at a solution

    I'm just wondering which sets of data points I should be using to calculate the velocity at 0.25 seconds: for example v=(0.25-0)/(0.29-0) is different from v=(0.50-0.25)/(1.15-0.29).
  2. jcsd
  3. Jan 4, 2014 #2
    Since the graph is linear between endpoints, select the points and compute the slope of the line, using the velocity equation you indicated and the endpoints of the line. Do the same for the second line, and you obtain the velocities.
  4. Jan 4, 2014 #3
    Sorry, but I don't really understand how to find the exact velocity at 0.25 seconds, since your method calculates the average velocity between 0s-0.25s.
  5. Jan 4, 2014 #4
    You would use v=(0.29-0)/(0.25-0) to get your best approximation to the velocity at 0.125, and you would use v=(1.15-0.29)/(0.5-0.25) to get your best approximation to the velocity at 0.375.
  6. Jan 5, 2014 #5


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    Staff: Mentor

    Hi terasnap, welcome to Physics Forums.

    There is no way to calculate the "exact" velocity at any moment, when all you have are a few data points. It is reasonable to assume that speed changes smoothly, so the data points you have should give their best approximation to the speed at those times midway between your data values. Calculate these values of velocity, and you can then use these figures to interpolate intermediate values of velocity.

    Chestermiller has shown you the way to begin.
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