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Lecture1

# Lecture1 - P309 Intermediate Physics Laboratory Lecture 1...

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P309 Intermediate Physics Laboratory Lecture 1: Experimental Uncertainties Reading: Squires “Practical physics”, pages 1-30 Handouts from http://physics.indiana.edu/~courses/p309/s09 “Experimental uncertainties” “Basic statistics” Mark Messier SW302, [email protected] 15 January 2008 1 Thursday, January 15, 2009

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“The” Scientific Method Experimental physics has as its essential goal the precise measurement of the parameters of the natural universe. These can then be compared to our models (“theories”) of the natural universe to select the models that most accurately represent reality. The key branch point in this process is this one: “Do measurement and theory agree?” As scientists, we need to be able to answer this question in an objective and quantitative way. As such, we need not only an accurate measurement but a reliable estimate of the uncertainty in that measurement. Example: Theory: Measure time for object to fall: Measurement Theory Do measurement and theory agree? Y N Theory lives! Continue testing with improved measurements Is measurement correct? Y Refine theory Continue testing with new and/or improved measurements N Refine experimental techniques “the” scientific method R E = 6 . 378 × 10 6 m M E = 5 . 974 × 10 24 kg G = 6 . 6743 × 10 - 11 m 3 / kg / s 2 g = GM E R 2 E = 9 . 8017 m / s 2 h = 3 . 0 m t = 0 . 80 s g = 2 x t 2 = 9 . 37 m / s 2 Do these agree? If uncertainty is ±0.5 then yes, they are consistent with each other If uncertainty is ±0.05, then no, they differ by a significant amount Experimenter has responsibility to provide not only the best estimate for the parameter being measured but also an accurate, quantitative estimate of the uncertainty in the value quoted 2
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Lecture1 - P309 Intermediate Physics Laboratory Lecture 1...

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