# PSU PHYS 250 - Knowledge of Nature (10 pages)

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## Knowledge of Nature

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## Knowledge of Nature

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Lecture Notes

Pages:
10
School:
Pennsylvania State University
Course:
Phys 250 - Introductory Physics I
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Measurement Models and Analysis Physics knowledge of nature Model an idealized description of a physical system or natural phenomena idealized how simplifications Measurements and Models qualitative vs quantitative descriptions interplay between observation measurements and the development refinement of model the scientific method Phys 250 Ch1 p1 Units and Standards of Measurement How big is A quantity has dimensions if the answer depends upon the units inches feet cm etc Basic Units or Fundamental Units are the standards by which measurement results are described Symbols for units can be used to help with dimensional analysis by treating unit symbols algebraically 10 Phys 250 Ch1 p2 m m m 5 s 50 s 50 s 50 m s s s Prefixes for units are convenient shorthand for scientific notation check out Phys 250 Ch1 p3 http www wordwizz com pwrsof10 htm http microcosm web cern ch Microcosm P10 english P0 html Examples A soccer field is supposed to be at least 100m x 64 m What is the area in kilometers squared of the smallest legal field What is the volume of a sheet of paper that is 21 6 cm by 27 9 cm and 8 6E 3 cm Phys 250 Ch1 p4 Consistency of units Algebraic equations must always be dimensionally consistent You can t add apples and oranges d vt distance speed time m 10 m 2 5 s s converting units treat units as algebraic quantities multiplying or dividing a quantity by 1 does not affect its value cm 1inch 2 540cm 2 540 1 inch cm 12inches 1 ft 1 ft 30 48cm 2 540 ft inch Phys 250 Ch1 p5 Some Useful Conversion factors 1 inch 2 54 cm 1 m 3 28 ft 1 mile 5280 ft Examples How many kilometers are in one mile If an automobile has a speed of 25 mi h what is its speed in km s Phys 250 Ch1 p6 Significant Figures common way of implicitly indicating uncertainty number is only expressed using meaningful digits sig figs last digit the least significant digit lsd is uncertain 3 one digit 3 0 two digits two significant figures 2 sig figs 3 00 three digits etc 300 how many digits Combining

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