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PHYS16 – Lecture 37

PHYS16 – Lecture 37. Ch. 16 Wave Motion. “Interference is much clearer in HD”. Oscillations pre-question. Is a bouncing ball an example of simple harmonic motion? Yes No. Oscillations pre-question.

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PHYS16 – Lecture 37

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  1. PHYS16 – Lecture 37 Ch. 16 Wave Motion “Interference is much clearer in HD”

  2. Oscillations pre-question • Is a bouncing ball an example of simple harmonic motion? • Yes • No

  3. Oscillations pre-question • Two kids are swinging on two swings of the same height – one kid is a little chubbier than the other. Neglecting frictional forces, which kid completes a back and forth swing in the fastest time? A) The chubby kid B) The skinny kid C) The kid who pushes off the ground the best D) Both complete in the same time

  4. Oscillations pre-question • A mass on a spring is driven at a driving frequency (red curve) and the resulting position vs. time of the mass is given (blue curve). Which case is closest to resonance?

  5. Ch. 16 Wave Motion • Mechanical Waves • Transverse vs. Longitudinal • Properties • Example: Wave on a String • How the wave propagates • Speed • Reflection and Transmission • Superposition and Standing Waves

  6. Waves pre-question PhET website

  7. Waves pre-question 0.0133 PhET website

  8. Mechanical Waves

  9. Mechanical Waves • A propagating oscillation that moves through a medium Transverse – water waves, disturbance on a string Longitudinal – sound waves, slinky or spring

  10. Mechanical Waves • Waves use at least 1-3 space dimensions and time… • Ex. – Water waves propagate in x, move “up and down” in y, and change position with time • Ex. – Sound waves propagate in x, move “up and down” in x, and change position with time

  11. Wave Properties • Period – high period medium period low period T

  12. Wave Properties • Period – • Wavelength and Wave number – http://seagrant.uaf.edu/marine-ed/curriculum/images/stories/grade7/wave.jpg

  13. Wave Properties • Period – • Wavelength and Wave number – http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific/wave_def.gif

  14. Wave Properties • Period – • Wavelength and Wave number – • Wave speed – http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific/wave_def.gif

  15. Ripple Tank Simulation

  16. Example: Speaker Speed = Period = Wave number = Wavelength = 330 m/s 0.0038 s 5.0m-1 1.25 m PhET website

  17. Example: Sand on a vibrating plate • Sand is placed on the vibrating plate below. Which apparatus is vibrating the plate with the highest wave number?

  18. Wave Function or Waveform Plane Wave Higher Dimension Wave

  19. Wave on a String

  20. Wave on a String • You can generate a wave on a string by pulsing sting with your hand • Speed of pulse/wave is related to tension in string and mass density of string PhET website

  21. Propagation of Pulse • If you advance the movie one frame point A will move… (higher, lower, right, left)? • If generate new pulse but more quickly than first then it will be… (same, wider, narrower)? • If generate new pulse but move hand higher than first then it will be… (same, taller, shorter)? • If generate new pulse with rope tightened then pulse will be… (same, faster, slower)? PhET website

  22. Wave on String Simulation PhET website

  23. Example Question PhET website

  24. Superposition, Interference, and Standing Waves

  25. Main Points – Wave Properties • Mechanical Wave – a propagating oscillation that moves through a medium • Period – • Wavelength and Wave number – • Wave speed –

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