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How do we calculate experimental errors?

  1. Nov 18, 2008 #1
    1. The problem statement, all variables and given/known data
    The problem lets us graph and give values for s(m) (distance) t(s) time and delta t (s) velocity. After plotting my second graph (including error bars) I used it to get the slope and the acceleration. But then it asks to determine the experimental error. Is there any formular for that? And how should I do it?


    2. Relevant equations
    That's what I want to know.


    3. The attempt at a solution
    Havne't done anything because I don't know what equations. It's urgent please help!
     
  2. jcsd
  3. Nov 18, 2008 #2

    LowlyPion

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    Homework Helper

    You need to estimate your measurement errors. What were the increments on the dials of the instruments you used. How might you have misread them if viewed from different angles. What other sources of error would make your readings less accurate. How do your results vary from theoretical considerations? Things like that.
     
  4. Nov 18, 2008 #3

    ShawnD

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    Science Advisor

    I don't specifically understand the question (I'm tired), but error is always calculated as:

    [(actual - calculated) / (calculated)] * 100 = %error

    If it seems tricky to remember, just remember that getting a low reading should give a negative error. This will help you remember how the numerator goes. The denominator is the calculated result so that you and your colleagues are all working on the same relative scale.

    Understanding why the equation is set like that will help you remember it.

    That's usually called a tolerance. The tolerance is a measure of your precision whereas error is a measure of accuracy.
     
  5. Nov 18, 2008 #4
    hmm... That's odd I didn't use any instruments, I'm not really understanding what they are asking for though. Do they mean the error of the VALUE of the acceleration I calculated? Or do they mean the error of the acceleration in the experiment itself?


    Well, if I'm not given the actual value, is there another way to get it?

    ----

    Most of the given question I poseted here https://www.physicsforums.com/showthread.php?t=272542 Everything is pretty much in there except that I didn't give all the values for the things.

    I'm pretty confused with this question as well, I've never done experimental errors, and I'll have to search my text one more time but it's confusing me because I'm in advance physics now, and this seems to be begining.
     
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