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Measurements in physics

Physics. Measurements in physics. - SI Standards (fundamental units) - Accuracy and Precision - Significant Figures - Uncertainties and Mistakes. Bell Ringer. Measuring with Metric.

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Measurements in physics

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  1. Physics • Measurements in physics - SI Standards (fundamental units) - Accuracy and Precision - Significant Figures - Uncertainties and Mistakes

  2. Bell Ringer

  3. Measuring with Metric We will take accurate measurements using appropriate instruments and the metric system & understand significant figures. I will complete a measurement lab & write significant figures rules DQ:How do significant figures relate to precision? *Use these numbers to explain. 1.0034 & 1.0

  4. AGENDA • Bell Ringer • Explore: Measurements Lab • Vocabulary: Accuracy& Precision, Uncertainties • Notes: Significant Figures • Examples/Worksheet

  5. Vocabulary • Metric • Precise • Accurate • Uncertainty

  6. Explore • Title: Measuring with Metric Lab • Purpose: The purpose of this lab activity is to practice taking accurate measurements using the metric system.

  7. Introduction: • To conduct a scientific investigation, a researcher must be able to make accurate measurements. In today’s exercise you will become familiar with metric system & units that scientists commonly use, and then you will take the measurements of some everyday objects.The metric system is the standard system of measurement in the sciences. It has tremendous advantages because all conversions, whether for volume, mass (weight), or length, are in units of ten.This ten-based system is similar to our monetary system, in which ____ cents equals a dime, and ____ dimes equals a dollar.

  8. Explore • With your group to complete the Lab & Worksheet. • You have 20 minutes to complete

  9. AGENDA • Bell Ringer • Explore: Measurements Lab • Vocabulary: Accuracy& Precision, Uncertainties • Notes: Significant Figures • Examples/Worksheet

  10. Measurements in physics - Precision and Accuracy “It’s better to be roughly right than precisely wrong” – Allan Greenspan, U.S. Federal Reserve Chairman (retired)

  11. Solution: Bell Ringer

  12. Accurate, Precise or Both?

  13. Answers

  14. Which is more precise?

  15. 1.1 Precision – how exact is a measurement, or how “fine” is the scale (# of significant figures). • 1.2 Accuracy – how close is the measurement to the “true” value. • Accuracy is a measure of the correctness of the measurement. • 2. Errors -We often want to know how close we are to the truth. The error is simply the quantifiable difference between the value obtained in real life and the “true” value.

  16. AGENDA • Bell Ringer • Explore: Measurements Lab • Vocabulary: Accuracy& Precision, Uncertainties • Notes: Significant Figures • Examples/Worksheet

  17. Introduction to Significant Figures

  18. Significant Figures Significant figures reflect precision. Two students may have calculated the acceleration due to gravity as 9.625 ms-2and9.8 ms-2respectively. The 1st is more precise; there are more significant figures but the last value is more accurate; it is closer to the correct answer.

  19. Significant Figures • Scientist use significant figures to determine how precise a measurement is • Significant digits in a measurement include all of the known digits plus one estimated digit

  20. For example… • Look at the ruler below • Each line is 0.1cm • You can read that the arrow is on 13.3 cm • However, using significant figures, you must estimate the next digit • That would give you 13.30 cm

  21. Let’s try this one • Look at the ruler below • What can you read before you estimate? • 12.8 cm • Now estimate the next digit… • 12.85 cm

  22. The same rules apply with all instruments • The same rules apply • Read to the last digit that you know • Estimate the final digit

  23. Let’s try graduated cylinders • Look at the graduated cylinder below • What can you read with confidence? • ___ ml • Now estimate the last digit • ____ ml

  24. Solution • Look at the graduated cylinder below • What can you read with confidence? • 56 ml • Now estimate the last digit • 56.0 ml

  25. One more graduated cylinder • Look at the cylinder below… • What is the measurement? • ____ml

  26. One more graduated cylinder • Look at the cylinder below… • What is the measurement? • 53.5 ml

  27. Note taking • Title- Rules for determining significant figures • Write each rule & an example.

  28. Rules for Significant figuresRule #1 • All non zero digits are ALWAYS significant • How many significant digits are in the following numbers? • 274 • 25.632 • 8.987

  29. Rules for Significant figuresRule #1 • All non zero digits are ALWAYS significant • How many significant digits are in the following numbers? • 3 Significant Figures • 5 Significant Digits • 4 Significant Figures • 274 • 25.632 • 8.987

  30. Rule #2 • All zeros between significant digits are ALWAYS significant • How many significant digits are in the following numbers? 504 60002 9.077

  31. Rule #2 • All zeros between significant digits are ALWAYS significant • How many significant digits are in the following numbers? 3 Significant Figures 5 Significant Digits 4 Significant Figures 504 60002 9.077

  32. Rule #3 • All FINAL zeros to the right of the decimal ARE significant • How many significant digits are in the following numbers? 32.0 19.000 105.0020

  33. Rule #3 • All FINAL zeros to the right of the decimal ARE significant • How many significant digits are in the following numbers? 3 Significant Figures 5 Significant Digits 7 Significant Figures 32.0 19.000 105.0020

  34. Rule #4 • All zeros that act as place holders are NOT significant • Another way to say this is: zeros are only significant if they are between significant digits OR are the very final thing at the end of a decimal

  35. 0.0002 6.02 x 1023 100.000 150000 800 For example How many significant digits are in the following numbers?

  36. 0.0002 6.02 x 1023 100.000 150000 800 1 Significant Digit 3 Significant Digits 6 Significant Digits 2 Significant Digits 1 Significant Digit For example How many significant digits are in the following numbers?

  37. Rule #5 • All counting numbers and constants have an infinite number of significant digits • For example: 1 hour = 60 minutes 12 inches = 1 foot 24 hours = 1 day

  38. 0.0073 100.020 2500 7.90 x 10-3 670.0 0.00001 18.84 2 Significant Digits 6 Significant Digits 2 Significant Digits 3 Significant Digits 4 Significant Digits 1 Significant Digit 4 Significant Digits How many significant digits are in the following numbers?

  39. Rule #6 • Rule for Addition or subtraction • 1. Add or subtract normally • 2. Your answer should have the same number of decimal places as the number with the least number of decimal places

  40. Example • 4.563 • + 3.12 • = 7.683 • Rounded to correct sig figs. • = 7.68

  41. Rule# 7 • Rule for multiplication or division. • 1. Multiply or divide normally • 2. Your answer should have the same number of sig figs as the number with the least number of sig figs

  42. Example • 2.32 • X 2.062 • = 4.78384 • Rounded to correct sig figs. • = 4.78

  43. AGENDA • Bell Ringer • Explore: Measurements Lab • Vocabulary: Accuracy& Precision, Uncertainties • Notes: Significant Figures & Examples

  44. END

  45. Bell Ringer

  46. Objectives

  47. AGENDA • Bell Ringer: Pre-Read; Cut & paste in Notebooks • Metric Mania Conversions (Dimensional Analysis) • Unit conversions scavenger Hunt • Intro to scientific notation: Note & examples

  48. Measurements in physics - SI Standards (fundamental units) Fundamental units: distance – meter (m) time – second (s) mass - kilogram (kg) temperature - kelvin (K) current – ampere (A) Amount of substance – mole (mol) – 6.02 x 1023 Derived units:combinations of fundamental units speed (v) = distance/time acceleration (a) = velocity / time force (F) = mass x acceleration energy (E) = force x distance charge (Q) = current x time units: m/s units: m/s/s= m/s2 units: kgm/s2 = N (Newton) units: kgm2/s2 = Nm = J (Joule) units: As = C (Coulomb)

  49. Intro to Scientific Notation • Use your IPad/electronic device to explore this section of the lab • 1. Explore the Universe in powers of 10! http://micro.magnet.fsu.edu/optics/tutorials/java/powersof10/ Step through the animation in manual mode. What is the power of 10 for each of the following? • Milky Way Galaxy: ___________ Stars in the Milky Way Galaxy: ________________ • Solar System: ______________ Earth and the Orbit of the Moon: _______________ • Southwest Tallahassee: __________ Oak Tree Branch: _________Cells on a Leaf: __________ • DNA Strand: __________ Nucleus of a Carbon atom: __________ Quark: ___________ • By what power of 10 is the Milky Way Galaxy larger than the Nucleus of a Carbon Atom? Show your calculation. Box your final answer.

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