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Homework Help: Relative uncertainty (negative exponent)

  1. Sep 8, 2016 #1
    1. The problem statement, all variables and given/known data
    A distance R is measured to be 3.400±0.003m. What is the relative uncertainty in R? 9×10-4
    What is the relative uncertainty in R^-2?
    2. Relevant equations


    3. The attempt at a solution
    Relative uncertainty of R is 0.003/3.4=8.8e-4
    Relative uncertainty of R^-2= -2(8.8e-4)=-1.76e-3?
    How do you calculate relative uncertainty with a negative exponent?
     
  2. jcsd
  3. Sep 8, 2016 #2

    mfb

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    2017 Award

    Staff: Mentor

    The relative uncertainy is always positive. The negative sign in your calculation indicates that a larger R leads to a smaller R-2, but that is not relevant here, so you have to take the magnitude.
     
  4. Sep 8, 2016 #3
    Thank you!
     
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