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Homework Help: Uncertainties of a group of results

  1. Oct 1, 2014 #1
    I got a table for a simple pendulum. I have 8 lengths, from 0.20m going up by 0.01 to 0.27. For each length, I have time for 10 oscillations (10T) that I've measured, and I have repeated the measurement twice for each length. Then I got the average time for 10T. I divided this average to give me an average for time period of one oscillation, T. I've plotted a graph of T2 against L, and so I also worked out T2 for each lengths' period time, T.

    I am stuck on the uncertainty. I have tired tried to work it out but when I do it for T I get 6.77%, and I do it for the spread of my results for T, but when I rise it to the power of 2 to get T2 its 45.89%. I can't have such a huge uncertainty. And also I am worried because it is uncertainty in measurement but I can firmly say that I didn't measure T but 10T, and so should I do the uncertainty for average 10T instead?

    What uncertainty would be the best to put down on my write up?

    I'm an A Level physics student.

    Thank you for all your help!
  2. jcsd
  3. Oct 2, 2014 #2


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    No way one can untangle this. 46 is the square of 6.8, but that's not the way errors propagate!
    Show your work.
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