Unit 3 - Physics. Motion. Intro to Measurements

Transcription

1 Unit 3 - Physics Motion Intro to Measurements

2 Physics Intro Activity - Interactive Station 1 cane balance/meter sticks Station 2 balance can Station 3 phone/calculator Flip Station 4 Chair lifting Station 5 Cereal magnet Station 6 Teabag Rocket

3 What is physics? What is Physics? cool physics tricks! Physics tricks! chair lifting myth? Phenomena of Physics pdmbpy#t= phenomena of Physics explained!

4 Things that make you go HMMMM.. CfukEgs What will hit the floor first a ball or feather dropped at the same time!

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6 Motion Physics Intro to MEASUREMENTS SIGNIFICANT FIGURES SCIENTIFIC NOTATION CALCULATIONS ACCURACY AND PRECISION ERRORS REVIEW OF METRIC SYSTEM

7 Significant figures and calculations

8 Significant figures in a measurement include all of the digits that are known, plus one more digit that is estimated. Which ruler is more precise? What is the estimated number in the following: A) 721 B)

9 Sig Fig App on TI-83/4 Calculators!

10 Significant Figures 1. Any digit that is not zero is significant (1,2,3,4,5,6,7,8,9) kg 4 significant figures 2. Zeros between non-zero digits are significant. 607 m 3 significant figures (AKA sandwiched zero s) 3. Leading zeros (to the left) are not significant L 1 significant figure g 3 significant figures 4. Trailing ( to the right) only count if there is a decimal in the number. 5.0 mg 2 significant figures. 50 mg 1 significant figure.

11 Two special situations have an unlimited number of Significant figures: 1.. Counted items a) 23 people, or 425 thumbtacks 2 Exactly defined quantities b) 60 minutes = 1 hour If asked on a test just put unlimited Sig Fig Song

12 Practice #1 For scientific notation, only look at the number before x10 x. How many significant figures in the following? m kg 100,890 L 3.09 x cm 3,200,000 ml 5 dogs 600. mm P. 349 # 1-3 Worksheet # 1 & 4 only

13 Rounding Calculated Answers Decide how many significant figures are needed Round to that many digits, counting from the left Is the next digit less than 5? Drop it. Next digit 5 or greater? Increase by rounded to hundredths is rounded to hundredths is rounded to hundredths is rounded to hundredths is rounded to hundredths is 62

14 Make the following have 3 sig figs: M Worksheet Sig. Fig s # 2 & 3 P. 349 #4 If you round to a whole number, add zero s to the end until it has the same place value as the original number!

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16 Significant Figures Using Addition and Subtraction The answer should be rounded to the same number of decimal places as the least number of decimal places in the problem. Examples: If you do not have a calculator, line up your decimals decimal places 3 decimal places 3 is the rounding number, and drop every number behind If units are used, ALWAYS include units in your answer!

17 Examples = = =

18 Multiplication and Division Round the answer to the same number of significant figures as the least number of significant figures in the problem. e.com/watch?v=o5b momdjlry

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20 Worksheet Adding and subtracting P. 349 #5,6

21 Scientific Notation

22 What is scientific Notation? Scientific notation is a way of expressing really big numbers or really small numbers. It is most often used in scientific calculations where the analysis must be very precise.

23 Why use scientific notation? For very large and very small numbers, these numbers can expressed in a more concise form. Numbers can be used in a computation with far greater ease.

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25 Scientific notation consists of two parts: 1. A number between 1 and 10 (1._ to 9._) 2. A power of 10 N x 10 x If whole number drop trailing zeros If decimal drop leading zeros but write every number remaining Positive exponent large # Negative exponent small # Got to have 1 counting number in front of the decimal.

26 Part I Changing standard form to scientific notation. N x 10 x

27 EXAMPLE # = If you do not see a decimalassume it is at the end To make the number smaller b/w 1._ and 9._ move to the LEFT positive exponent Note drop any trailing zeros must keep counting numbers or sandwiched zeros

28 EXAMPLE # = Numbers less than 1 will have a negative exponent. Note drop any leading zeros must keep counting numbers or sandwiched zeros that come after the decimal

29 TRY THESE Express in scientific notation 1) ) ) )

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31 Part II CHANGE SCIENTIFIC NOTATION TO STANDARD FORM 2.35 x 10 8

32 To change standard form to scientific notation Place the decimal point so that there is one non-zero digit to the left of the decimal point. Count the number of decimal places the decimal point has moved from the original number. This will be the exponent on the 10.

33 Continued If the original number was less than 1, then the exponent is negative. If the original number was greater than 1, then the exponent is positive.

34 EXAMPLE #1 9.0 x 10-5

35 TRY THESE Change to Standard Form 1) 4.21 x ) 0.06 x ) 5.73 x ) x 10-5 In Class assignment up to here

36 If you can t round to the correct number of significant figures using standard form.try scientific notation!! Not usually done but can get out of a sig. fig. bind!!

37 Metric Conversions Ladder Method

38 Unit Conversion 1. Base Units Length (distance) meter (m) Time second (s) Mass gram (g) Electric Current ampere (A) Volume litre (L)

39 Pneumatic memorizing device

40 Metric Prefixes

41 KILO 1000 Units 1 2 HECTO 100 Units Ladder Method DEKA 10 Units Meter s Liters Gram How do you use the ladder method? s 1 st Determine your starting point. 2 nd Count the jumps to your ending point. 3 rd Move the decimal the same number of jumps in the same direction. 3 DECI 0.1 Unit CENTI 0.01 Unit MILLI Unit 4 km = m Starting Point Ending Point How many jumps does it take? = 4000 m

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43 Ladder Method for Base Units KILO 1000 Units HECTO 100 Units DEKA 10 Units DECI 0.1 Unit CENTI 0.01 Unit MILLI Unit 1st Determine your starting point. 2nd Count the jumps to your ending point. 3rd Move the decimal the same number of jumps in the same direction.

44 Metric Conversion Challenge Write the correct abbreviation for each metric unit. 1) Kilogram 4) Milliliter 7) Kilometer 2) Meter 5) Millimeter 8) Centimeter 3) Gram 6) Liter 9) Milligram Try these conversions, using the ladder method. 10) 2000 mg = g 15) 5 L = ml 20) 16 cm = mm 11) 104 km = m 16) 198 g = kg 21) 2500 m = km 12) 480 cm = m 17) 75 ml = L 22) 65 g = mg 13) 5.6 kg = g 18) 50 cm = m 23) 6.3 cm = mm 14) 8 mm = cm 19) 5.6 m = cm 24) 120 mg = g

45 Convert using the ladder method: 1000 mg = g 1 L = ml 160 cm = mm 14 km = m 109 g = kg 250 m = km Compare using <, >, or = 56 cm 6 m 7 g 698 mg Conversion Worksheet #1

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47 Derived Units (SI) Calculated Quantities Derived Quantity Symbol Speed & Velocity m/s Acceleration m/s 2 Area m 2 Volume m 3

48 Changing around formulas to solve for certain values. Completing at a later date

49 Unit Analysis for Calculated (derived) Units Ex: Convert 100 km/hr to m/s. Main goal is to cross out or reduce unit until you get the desired ones

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52 You will need to know time conversions. 1 year= 365 days leap year is year = 52 weeks 1 week = 7 days 1 day = 24 hours 1 hour = 60 minutes 1 min = 60 seconds How many seconds are in 2 years? Text P. 349 #9 a-d and P. 356 #5 & 6 Conversion Worksheet #2

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56 Accuracy & Precision Accuracy refers to the closeness of measurements to each other i.e. how close a measured value is to the actual (true) value. Precision is how close the measured values are to each other /whats-the-difference-between-accuracyand-precision.aspx

57 Accuracy or Precision Precision Reproducibility of results Several measurements afford the same results Is a measure of exactness Accuracy How close a result is to the true value Is a measure of rightness

58 Which ruler is more precise? Pencil A: Pencil B The smaller the unit you use to measure with, the more precise the measurement is.

59 Accuracy vs Precision π Accuracy Precision 3 NO NO NO YES 3.14 YES NO YES YES

60 Sources of Error 1. Random (human) Error An error that relates to reading a measuring device. Ex: Estimating the last digit when reading a ruler. Random error can be reduced by taking many measurements and then averaging them.

61 2. Systematic Error An error due to the use of an incorrectly calibrated measuring device. Ex: a clock that runs slow or a ruler with a rounded end. Can be reduced by inspecting and recalibrating equipment regularly.

62 3. Parallax An error due to your viewing angle of a measurement. Ex. How much gas you think you have left in the tank depends on where you are sitting.

63 What type of error is it??? 1. You measure the mass of a ring three times using the same balance and get slightly different values: g, g, g. 2. The meter stick that is used for measuring, has a millimetre worn off of the end therefore when measuring an object all measurements are off.

64 % Error (ie: % Discrepancy) The difference between the value determined by your experimental procedure and the generally accepted value. The simplest way to express accuracy mathematically.

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66 Example: Deadpool estimates the time it will take him to heal from his last battle with T-Ray to be 45.8 minutes. It actually takes him 53.6 minutes. Calculate the percent error.