Today s Class Oscillators and Waves

Transcription

1 Today s Class Oscillators and Waves A college-freshman physics lab Heuristics, Measurements, Analysis A full tour of AZ / Next-Gen Science Standards (OPAC) Observe, ask questions, make predictions Plan and conduct investigations, record data Analyze data, compare to predictions Communicate results of investigations The physics of the pendulum, a simple oscillator 1

2 Observe the Pendulum A Simple Oscillator The period of the pendulum is the time it takes to make one round trip (cycle), out and back. 2

3 Plan: Write down 3 hypotheses about the period of the pendulum The period depends on displacement Accept? / Reject? (Galileo) The period depends on mass Accept? / Reject? Clear Start Stop The period depends on length Accept? / Reject? Let s Find Out!! 3

4 We Just Repeated Galileo s Experiment! 1602 Galileo is 20 yrs old He s sitting in church in Pisa, Italy He s bored!! He sees a lamp swinging overhead He times the swings with his pulse Large swings or small, he observes the period is always the same! Fascinated, he later derives the law of the pendulum 4

5 Plan and Analyze So period depends on length, but how does it depend on length? Plan, make period measurements for different-length pendulums Record the data in a table Analyze our data, using graphs 5

6 Names: Team: Date: My Pendulum Data Measure Measure Compute Length (cm) 10 Periods (secs) 1 Period (secs) Choose lengths no less than 10.0 cm and no greater than cm. Compute the last column just divide number in 2nd column by 10. 6

7 Making Measurements & Recording Data Aksel, Maren, & Devlan Jan 15,

8 T Name: Date: 32, 1.15

9 Plotting Data Looking for Trend 9

10 Math Formula for Pendulum Period T (secs) versus L (cm) Good Approximation: 10

11 T Names: Team: Date: 32, 1.15

12 Compare Results to Theory 12

13 Quick Review of Oscillators Oscillators alternately store and release energy For the pendulum, we can see the store/release cycle Kinetic (motion) and potential (position) energy Oscillators can also make WAVES Audio waves, also called acoustic waves Radio waves, also called electromagnetic waves 13

14 Oscillators & Waves Energy, Frequency, Vibration

15 Tuning Fork Oscillator: Sound Waves Period = secs Frequency = 1/ = 256 Hertz Resonance sine wave 15

16 Making and Seeing Audio (Sound) Waves Oscilloscope and Spectrum Analyzer 16

17 Wine Glass Audio Oscillator 17

18 Resonance Breaks a Wine Glass! 18

19 Coke Bottle Oscillator 19

20 Music on Beer Bottles 20

21 Why Oscillators Matter Tacoma Narrows Bridge Failure!! 21

22 Slinky Demo Electrons on a Wire Antenna Electromagnetic Waves Radio and Light 22

23 Make Your Own Straw Oboe 23

24 What Have We Studied? How to apply the scientific method Orderly creation of hypotheses Creation of experiments to accept or reject hypotheses Practical measurements of time and length Graphing fundamentals why graphs help Comparing measured results to theoretical results Reporting of results 24

25 Science Vocabulary Hypothesis Pendulums, Oscillators Kinetic, Potential energy Period, Frequency Formulas and Laws Waves Acoustic (audio) Resonance Waves Electromagnetic (radio, light).. 25

26 Accuracy and Precision In Science, They re Different! Example: GPS Positioning Accuracy vs Precision A B C D 26

27 Paper Forms 27

28 Names: Team: Date: My Pendulum Data Measure Measure Compute Length (cm) 10 Periods (secs) 1 Period (secs) Choose lengths no less than 10.0 cm and no greater than cm. Compute the last column just divide number in 2nd column by

29 Names: Team: Date: T

30 Name: Date: T

31 ASL Class: Oscillators and Waves Class Features Overview Built upon 2013 Next Generation Science Standards Framework Features hands-on lab with all four NGSS Framework themes 1. Observe, Question, Predict 2. Plan, Measure, Record 3. Analyze, Compare, Conclude 4. Communicate, Report Based on college-physics pendulum lab, adapted for grades 4-9 Teaches basic science concepts about oscillators and waves, e.g., Oscillators store & release energy we can watch (child on swing) Oscillators make audio waves that we can hear Oscillators make radio waves that we can send through space Increased activity & demos, reduced slide-based lecture time: Conduct experiments to accept or reject hypotheses about pendulum Measure time & distance, reduce errors by averaging Apply stopwatch, meter stick, calculator, graph paper Create one-page lab report 31

32 Sequence of Events Lab Part 1 Observe movie clip of child on swing Free-form questions and predictions whole class Our question: What determines time per swing (period)? How heavy (mass)? How far (displacement)? How long (length)? Practice time measurements as a class Construct one lab pendulum per 3-student team Test hypothesis that displacement matters; accept/reject Test hypothesis that mass matters; accept/reject Test hypothesis that length matters; accept/reject 20 minutes mins Free-form investigation meter stick, stopwatch, calculator supplied poll tables for results Real data -- discover the Law of the Pendulum Measure period vs length, record data Stopwatch, meter stick - average of 10 swings for 3-5 different lengths Plot data on X-Y graph paper (supplied with labeled axes) Re-plot data on X-Y graph paper atop theoretical curve (supplied) Report Discuss sources of error mins incl discussion more structured 32

33 Oscillators and Waves Lab Part 2 Audio (sound) oscillators and waves Demonstrations: Tuning forks, bells, wine glasses, and musical instruments Electronic audio oscillators Period (seconds) vs Frequency (Hz or roundtrips/second) Seeing sound waves: Oscilloscope Demo Spectrum Analyzer Demo Build a simple reed instrument from a soda straw Brief intro to radio & light waves (advanced) Electromagnetic waves How an AM radio works in pictures and demos Build a simple AM receiver 33

34 What Have We Studied? How to apply the scientific method Orderly creation of hypotheses Creation of experiments to accept or reject hypotheses Practical measurements of time and length Data recording and averaging to improve accuracy Graphing fundamentals why graphs help Comparing measured results to theoretical results Reporting of results 34

35 Speaking of Science Hypothesis Pendulums, Oscillators Kinetic, Potential energy Period, Frequency Formulas and Laws Waves Acoustic (audio) Resonance Waves Electromagnetic (radio, light).. 35

36 Appendix 36

37 AZ & National Science Standards Frameworks AZ Science Stds Grades Observe, ask questions, make predictions NGSS Asking questions and defining problems 2. Developing and using models 2. Plan and conduct investigations, record data 3. Organize & Analyze data, compare to predictions 4. Communicate results of investigations 3. Planning and carrying out investigations 4. Analyzing and interpreting data 5. Using mathematics, information and computer technology, and computational thinking 6. Constructing explanations and designing solutions 7. Engaging in Argument from evidence 8. Obtaining, evaluating, and communicating information

38 Names: Date: T

39 Names: Date: T

40 Graphing Data 1 st Handout Plot Measured Results 2nd Handout Replot and compare to the Law of the Pendulum

41 ASL Pendulum Lab Materials 41

42 Fitting an ASL Class to the NGSS *The Framework identifies eight science and engineering practices that mirror the practices of professional scientists and engineers. These are intended to strengthen students skills in these practices at the same time as they develop their understanding of the nature of science and engineering. Listed below are the science and engineering practices from the Framework: 1. Asking questions and defining problems 2. Developing and using models 3. Planning and carrying out investigations 4. Analyzing and interpreting data 5. Using mathematics, information and computer technology, and computational thinking 6. Constructing explanations and designing solutions 7. Engaging in Argument from evidence 8. Obtaining, evaluating, and communicating information *June, 2013 NGSS Front Matter 42

43 Fitting an ASL Class to the Current AZ Science Standard ( Grade 4 Strand 1 Observe, ask questions, make predictions. Plan and conduct investigations, record data Organize and analyze data, compare to predictions Communicate results of investigations Grade 8 Strand 1 Form predictions, questions, hypotheses from observations Design and conduct controlled investigations Interpret data, explain correlations, form new questions Communicate results of investigations Almost identical, Grades 4-8! 43

44 Making Measurements & Recording Data 44

45 Plotting Data Looking for Trend 45

46 Compare Results to Theory 46