Chapter 15 Supplement HPS. Harmonic Motion

Transcription

1 Chapter 15 Supplement HPS Harmonic Motion

2 Motion Linear Moves from one place to another Harmonic Motion that repeats over and over again Examples time, speed, acceleration Examples Pendulum Swing Pedaling on a cycle

3 Harmonic Motion Nature Art / Music Technology Pendulum Heart Electrons Earth - 4 oscillators Light Sound Color in light waves Cell phones Radio waves Clocks

4 Evidence of WAVES See vibrations Makes or responds to sound or lights Transmits info through the air w/o wires Allows you to see through objects

5 Electromagnetic spectrum

6 2 Types of Waves Transverse Oscillate perpendicular to the direction of the wave Ex: water Longitudinal Oscillate parallel to the direction of the wave Ex: compressional

7 Properties of Waves Amplitude: the height of the wave (m) Wavelength: the distance between adjacent crests (m) Period: the time it takes for one complete wave to pass a given point (sec.) Frequency: the number of complete waves that pass a point in one second (1/sec or Hz) Speed: the horizontal speed of a point on a wave as it propagates (m/sec) (frequency x wavelength)

8 Properties of Waves Crest S Trough

9 Terms Harmonic motion is a repeated sequence of cycles. Period time for 1 cycle. (sec.) Frequency - # cycles per second. (Hz) Amplitude Size of the cycle (degrees, length, voltage, pressure)

10 Basic characteristics of waves Node Points where the string does not move Anti-node Points where the string moves the most What harmonic?

11 RESONANCE These Standing Waves occur at what are called Natural Frequencies or Harmonics Every object, substance and material has its own Natural Frequencies, where it likes to vibrate All Natural Frequencies are multiples of the Fundamental

12 Natural Frequency Know how it will vibrate Know what kind of waves it makes Depends Tension length weight of string Resonance Having the natural frequency just in tune with your force Each force adds to the system Transfer of Power Swing Each pump adds to the last and the amplitude grows

13 Tacoma Narrows Bridge months after completion Destroyed by wind generated resonance Mild gale produced an irregular force in resonance with the natural frequency of the bridge, steadily increasing the amplitude of vibration until the bridge collapsed.

14 Interference

15 Patterns on the String Standing Wave Patterns Calculate Wavelength? (λ)

16 Lab: v = f λ Each Harmonic has a different frequency and wavelength Hz x λ gives the same answer for ALL Harmonics Cycles/Seconds x Meters/Cycle= Meters/Second which is a value for speed of the Wave on the string If Frequency Wavelength and if Frequency, Wavelength T = 1/f

17 Harmonic Motion Graphs energy / amplitude? Independent variable: Dependent variable: X- axis: Y-axis:

18 Damping What causes the damping in each situation?

19 Damping

20 ENERGY INTERATIONS ABSORPTION REFLECTION DIFFRACTION REFRACTION

21 ENERGY INTERATIONS ABSORPTION REFLECTION DIFFRACTION REFRACTION

22 ENERGY INTERATIONS ABSORPTION REFLECTION DIFFRACTION REFRACTION

23 ENERGY INTERATIONS ABSORPTION REFLECTION DIFFRACTION REFRACTION

24 Chapters 15.3 & 16.1 HPS Sound & Waves

25 Range ,000 Hz HIGH Hairs EAR DRUM Fluid-Filled Hearing and Balance Best Range ,000 Hz LOW

26 LAB DEMO: FEEL THE AMPLITUDES (1) FREQUENCY CHANGES and (2)VOLUMES Radio loudspeaker is a paper cone that vibrates in rhythm with an electrical signal. (wavelength) Air molecules are set into motion vibrating into other molecules. They vibrate from the speakers into the room setting the room air molecules into motion which collide into our eardrum. Speakers

27 Lab Properties of Sound Section 1 (Teacher demonstrated LAB) Consonance Sounds GOOD Dissonance Sounds BAD

28 Answer: BEATS (DISSONANCE) Results when 2 frequencies are close

29 Lab DEMO Properties of Sound WAVELENGTH Section 2 Sound gets louder then softer WHY? (constructive and destructive interference) Move speaker forward

30 IN PHASES OUT

31 Partially out of Phase Softer Sound

32 - High Freq. Frequency and Pitch - High Pitch - Waves closer together - Low Freq. - Low Pitch - Waves farther apart

33 Lab 13.2 Properties of Sound Section 3 Which has a HIGHER Frequency? Which has a LOWER frequency? A B C

34 Lab 13.2 Properties of Sound Section 3 Which had a HIGHER Frequency? Which had a LOWER frequency? A B C

35 Lab 13.2 Properties of Sound Section 5 Which wine glass had a HIGHER frequency? LOWER frequency? What is vibrating?

36 Lab 13.2 Properties of Sound Section 5 Which wine glass had a HIGHER frequency? LOWER frequency? What is vibrating? WATER

37 Lab 13.2 Properties of Sound Section 6 Which bottle had a HIGHER frequency? LOWER frequency? What is vibrating?

38 Lab 13.2 Properties of Sound Section 6 Which bottle had a HIGHER frequency? LOWER frequency? What is vibrating? AIR

39 Air Pressure Loud High Pressure HARMONIC MOTION is an oscillation in pressure and the wave produced is a sound wave. Soft Low Pressure

40 Decibel Scale (db) Measures loudness Relates to amplitude of the wave Most sound between Every 10dB increase sounds about 2xs as loud

41 Sound Waves Alternating high and low pressure Anything that vibrates creates sound waves Longitudinal Wave (air is compressed) The speed of sound in other materials is often faster than in air. No sound in outer space.

42 Speed 340 m/s (660 mph) Depends on Temperature Cold / slower Hot / faster Kind of molecule Heavier / slower Lighter / faster Restoring Force Smaller / slower Bigger / faster Speed of Sound Waves

43 Supersonic Speed Motion faster than sound Passenger jet - Concorde SHOCK WAVE NOISE! QUIET

44 Acoustics The science and technology of sound Reflection Diffraction Absorption Each of these can be done with a certain degree of success To stop sound dense thick wall materials

45 Concert Halls Reverberation multiple echo results when waves bounce off of hard surfaces The right amount is good sound livelier and richer Also causes interference could result in dead spots (destructive interference)

46 Fundamental Harmonic (A) Frequency and Sound (A) (B) 2 nd (B) 3 rd (C) 4 th (D) Amplitude (cm) (C) (D) 5 th (E) (E) Frequency (Hz)

47 Understanding Sound Waves SONOGRAMS Graph that shows how loud sound is at different freq. Freq (Hz) ULTRASOUND High Freq creates images of body Time (sec) WHITE NOISE Equal mixtures of all frequencies

48 END

49 Note Name Frequency C major C minor D major C 264 Yes Yes D flat 285 D 297 Yes E flat 317 Yes E 330 Yes F 352 G flat 380 Yes G 396 Yes Yes A flat 422 A 440 Yes B flat 475 B 495 C 528 Optional Optional T u n i n g N o t e s f o r C h o r d s

50 Sound and Music - Chords Different notes have different frequencies Chords are combinations of different notes with specific mathematical relationships Different relationships of the notes will produce chords with very different moods or feel

51 Note Name Key Color Frequency C 528 B 495 B flat 475 A 440 A flat 422 G 396 G flat 380 F 352 E 330 E flat 317 D 297 D flat 285 C 264

52 HAPPY BIRTHDAY Melody C C D C F E C C D C G F Harmony A A B b B b B b A Melody C C C A F E D B b B b A F G F Harmony F C B b C A

53 TWINKLE, TWINKLE LITTLE STAR Melody F F C C D D C B b B b A A G G F Harmony C C A A B b B b A G G F F E E C Melody C C B b B b A A G C C B b B b A A G Harmony A A G G F F C A A G G F F C Melody F F C C D D C B b B b A A G G F Harmony C C A A B b B b A G G F F E E C

54 GOD BLESS AMERICA Melody F E D E D C G F G A G A B b D Harmony A C E E D E F D Melody B b A C F G A G F G F E F Harmony C F E C Melody E F G C F G A C G A B b E A B b C Harmony C E D F E G C G Melody D C B b A G F B b A G F Harmony F F E C E D F F E C