Vibrations and Waves

1. Chapter 18 Vibrations and Waves

3. Simple Harmonic Motion to-and-fro vibratory motion results in sine curves Examples: Metronome

4. Simple Harmonic Motion to-and-fro vibratory motion results in sine curves Examples: mass on a spring

5. Simple Harmonic Motion to-and-fro vibratory motion results in sine curves Examples: pendulum

6. Pendulums The period does not depend on the amount of mass. The period does depend on the length of the pendulum.

7. Wave Comparisons Water Waves Sound Waves Light Waves Waves Medium Wave Speed What if you go faster? Human Perception

8. Vibrations and Waves Oar in Water Wings of a Bee Electrons in an Light Bulb

9. Wave Description Period - the time required for one vibration measured in seconds Frequency - number of vibrations / unit time measured in Hertz

10. Wave Description

11. Example Test Question: If you double the frequency of a vibrating object, what happens to the period? a) the period doubles b) the period stays the same c) the period is cut in half d) not enough information is given to answer this question.

12. What is the frequency in vibrations per second of a 60-Hz wave? Answer: 60 cycles per second What is its period? Answer: 1/60 second

13. Sine Curves Amplitude - distance from the baseline to the crest of a wave Wavelength - the distance from the top of one crest to the top of the next one

15. Wave Motion medium - the stuff that carries the wave

16. Wave Speed Speed with which waves pass by a particular point e.g. the speed of a surfer Depends only on the type of medium Wave Speed = Frequency ? Wavelength m/s = cycles/s x meters/cycle

17. If a water wave oscillated up and down three times each second and the distance between wave crest is 2 m, what is its frequency? Answer: 3 Hz What is its period? Answer: 1/3 second What is its wavelength? Answer: 2 m What is its wave speed? Answer: 6 m/s

18. Transverse Waves Side to side vibration in a direction perpendicular to the wave's motion Examples: water waves waves on a rope string musical instruments

19. Longitudinal Waves back and forth vibration in a direction parallel to the wave's motion Examples: slinky waves sound waves

21. Example Question The distance from trough to trough on a periodic wave is called its... a) frequency. b) period. c) wavelength. d) amplitude.

22. Example Question Changing which of the following affects the period of a pendulum? a) mass b) amplitude c) length d) angle

23. Example Question Dipping a finger in water faster and faster causes the wavelength of the spreading waves to a) increase b) decrease c) stay the same d) not enough information is given

24. INTERFERENCE Constructive or destructive interference results when waves add. Standing Waves - wave pattern produced from interfering waves Examples Rope Waves Guitar Strings Bell Wave Machine Organ Pipe

26. DOPPLER EFFECT the change in frequency due to motion of the source "Wheeeeeeeeeeee�.Oooooooooooooo� Coming towards you � higher frequency Going away from you � lower frequency Examples: moving cars and trains rotating whistle

27. - slower than the speed of sound Subsonic Supersonic

28. Shock Wave

35. Example Question A train whistle at rest has a frequency of 3000 Hertz. If you are standing still and observe the frequency to be 3010 Hertz, then you can conclude that... a) the train is moving away from you. b) the train is moving toward you c) the sound from the whistle has echoed d) not enough information is given

36. Example Question Changing which of the following affects the period of a pendulum? a) mass b) amplitude c) length d) angle

37. Example Question Dipping a finger in water faster and faster causes the wavelength of the spreading waves to a) increase b) decrease c) stay the same d) not enough information is given

38. Example Question The distance from trough to trough on a periodic wave is called its... a) frequency. b) period. c) wavelength. d) amplitude.