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Propogation of uncertainty in a data set (finger-math at most)

  1. Sep 30, 2012 #1
    1. The problem statement, all variables and given/known data
    I have conducted a simple lab, that involves getting the distance traveled by a vertically falling weight at certain time intervals. Velocity is calculated for every time interval (distance traveled per time interval). Then I graph velocity versus time to get acceleration which comes out decently close to g.

    Now the part I am confused about is calculating uncertainty for:
    a) Velocity
    b) Acceleration
    c) y-intercept of velocity vs. time graph (acceleration line)

    Absolute uncertainty for time is +-0.010s, and +-0.001m (1mm) for distance.

    2. Relevant equations
    Relative uncertainty % = Absolute Uncertainty / Measured value
    * and / of uncertainties with each other adds their relative uncertainties

    3. The attempt at a solution
    Since this is of a data set, you have many measured values, and it makes no sense to have a single relative uncertainty in the above equation. It would be different for each data point, correct?

    Am I missing something from this concept? Or do I literally have to calculate out a different uncertainty for each velocity? Another possibility could be finding relative uncertainty for the first data point and using that % throughout the problem for all of them but that cant be right...
     
  2. jcsd
  3. Oct 1, 2012 #2
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