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Science, Measurements, Uncertainty and Error

Science, Measurements, Uncertainty and Error. Conversion of Units. Conversion Factor. A conversion factor is a ratio between two units:. The conversion factor can be written with either value on top, just set it up so that things cancel out!. Example. How fast is 100 km/h in m/s?.

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Science, Measurements, Uncertainty and Error

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  1. Science, Measurements, Uncertainty and Error Science, Measurement, Uncertainty and Error

  2. Conversion of Units

  3. Conversion Factor A conversion factor is a ratio between two units: The conversion factor can be written with either value on top, just set it up so that things cancel out!

  4. Example How fast is 100 km/h in m/s? 27.777...m/s Write what you have… multiply by conversion factor(s)… do the math… multiply the tops, multiply the bottoms, then divide these 2 #’s

  5. Example How fast is 50mph in m/s? 22.3472 m/s Write what you have… multiply by conversion factor(s)… do the math… multiply the tops, multiply the bottoms, then divide these 2 #’s

  6. Uncertainty in Measurement and Significant Figures

  7. http://smedia.vermotion.com/media/12933/resources/60000.JPG http://www.gototem.com/Webgifs/ClipArt/Sports/Darts.GIF Precision The darts are all close to one another. They may or may not be close to the intended target.

  8. http://smedia.vermotion.com/media/12933/resources/60000.JPG http://www.gototem.com/Webgifs/ClipArt/Sports/Darts.GIF Accuracy Dart is right on target. (The value is close to what it should be.)

  9. Precision How reproducible are measurements? Accuracy How close are the measurements to the true value. Precision and Accuracy in Measurements

  10. Dartboard analogy • Imagine a person throwing darts, trying to hit the bulls-eye. Not accurate Not precise Accurate Not precise Not accurate Precise Accurate Precise

  11. Scientific Data The precision and accuracy are limited by the instrumentation and data gathering techniques. Scientists always want the most precise and accurate experimental data.

  12. Dealing with Errors • Identify the errors and their magnitude. • Try to reduce the magnitude of the error. HOW? • Better instruments • Better experimental design • Collect a lot of data

  13. Counting Sig Fig’s – 4 Rules: Nonzero digits are always significant All final zeros after the decimal point are significant Zeros between two other significant digits are always significant Zeros used solely as placeholders are not significant

  14. Counting Sig Fig’s – Sci. Notation Use Scientific Notation… Determine how many digits are important when writing the number in scientific notation.

  15. How many significant figures? 1,460 3

  16. How many significant figures? 21.76 4

  17. How many significant figures? 421.03 5

  18. How many significant figures? .002 1

  19. How many significant figures? 1,000.1 5

  20. How many significant figures? 726.01 5

  21. How many significant figures? 720 2

  22. How many significant figures? 4.801 4

  23. How many significant figures? 0.103 3

  24. How many significant figures? 0.000827 3

  25. How many significant figures? 1.47 3

  26. How many significant figures? 1,200 2

  27. How many significant figures? 1,200,000.0 8

  28. How many significant figures? 120 2

  29. How many significant figures? 4.60 3

  30. How do you round? Rounding is different, depending on whether you are adding or subtracting OR multiplying or dividing

  31. Adding/Subtracting Add/Subtract first Round according to the fewest number of Digits After the Decimal

  32. Examples: 286.9 2.251 507.8

  33. Multiplying/Dividing Multiply/Divide first Round according to the fewest number of Significant Figures

  34. Examples: 12,000 92 380

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