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Combining uncertainties

  1. Mar 17, 2007 #1
    1. The problem statement, all variables and given/known data
    If the uncertainty in a measurement of dameter is +-0.02cm is the uncertainty in radius the same or half of this value. The formula given in wikipedia implies that it would be half of the value.


    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 17, 2007 #2


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    Yes, it will be half of this value. If the uncertainty had been given in percent form, then the percent uncertainty on the radius and on the diameter would be the same.
  4. Mar 17, 2007 #3
    you should had this formula in your relevant equations thingy:
    radius = diameter /2

    2 is a number, and has uncertainty of 0
    so, use division rule
  5. Mar 17, 2007 #4
    Ok thanks guys.
    I now have to work out the uncertainty in the voume of a sphere using the radius I have. Any clues on how to get the uncertainty in this value? I would expect that it would be bigger but I can't really understand why?
  6. Mar 17, 2007 #5
    I have this formula


    Is this correct?
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