1. 17.2 Properties of Mechanical Waves continue notes from 17.1 in same day...

2. 17.2 Properties of Mechanical Waves A surfer needs to understand the properties of waves.

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Characteristics of a Wave Section 2 - Properties of WAVES Chapter 17 Click below to watch the Visual Concept then click play. Come back by using command and tab key OR click on keynote icon. Visual Concept http://my.hrw.com/sh/hk6_0030390966/student/ch14/sec02 /vc00/hk614_02_v00fs.htm

4. 17.2 Properties of Mechanical Waves Any motion that repeats at regular time intervals is called periodic motion. The time required for one cycle is called the period. (ex. ocean waves - period is time between 2 successive crests or troughs.) Frequency and Period

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Wave Period of Ocean Waves Section 2 Characteristics of Waves Chapter 17 Click below to watch the Visual Concept. Visual Concept http://my.hrw.com/sh/hk6_0030390966/stude nt/ch14/sec02/vc02/hk614_02_v02fs.htm

6. 17.2 Properties of Mechanical Waves Frequency and Period What determines the frequency of a wave? Any periodic motion has a frequency, which is the number of complete cycles in a given time. Frequency is the number of complete cycles in a given time. Frequency is measured in cycles per second, or hertz (Hz). A wave’s frequency equals the frequency of the vibrating source producing the wave.

7. 17.2 Properties of Mechanical Waves A. A wave vibrating at one cycle per second has a frequency of 1.0 Hz. B. A wave vibrating at two cycles per second has a frequency of 2.0 Hz. Frequency and Period Frequency = 1.0 hertz One cycle per second Frequency = 2.0 hertz Two cycles per second

8. 17.2 Properties of Mechanical Waves Wavelength How are frequency and wavelength related? Wavelength is the distance between a point on one wave and the same point on the next cycle of the wave. Increasing the frequency of a wave decreases its wavelength.

9. 17.2 Properties of Mechanical Waves For a transverse wave, wavelength is measured between adjacent crests or between adjacent troughs. For a longitudinal wave, wavelength is the distance between adjacent compressions or rarefactions. Wavelength

10. 17.2 Properties of Mechanical Waves Wavelength can be measured from any point on a wave to the same point on the next cycle of the wave. Increasing the frequency of a wave decreases its wavelength. (Draw the following and label...) Wavelength Long wavelengthShort wavelength Rest position Trough crest amplitude I

11. 17.2 Properties of Mechanical Waves Wave Speed How are frequency, wavelength, and speed related?

12. 17.2 Properties of Mechanical Waves When the wavelength is in meters, and the frequency is in hertz, the units for speed are meters per second. The speed of a wave is also calculated by dividing its wavelength by its period. v= λ/t Wave Speed v = λ x f v= λ/t RECORD BOTH EQUATIONS!

13. 17.2 Properties of Mechanical Waves The speed of a wave can change if it enters a new medium, or if variables such as pressure and temperature change. For many kinds of waves, the speed of the waves is roughly constant for a range of different frequencies. The wave with the lower frequency has a longer wavelength. Wave Speed If you assume that waves are traveling at a constant speed, then wavelength is inversely proportional to frequency.

14. 17.2 Properties of Mechanical Waves Speed of Mechanical Waves One end of a rope is vibrated to produce a wave with a wavelength of 0.25 meter. The frequency of the wave is 3.0 hertz. What is the speed of the wave? Wave Speed

15. 17.2 Properties of Mechanical Waves Read and Understand What information are you given? Wave Speed

16. 17.2 Properties of Mechanical Waves Read and Understand What information are you given? Wave Speed

17. 17.2 Properties of Mechanical Waves Plan and Solve What unknown are you trying to calculate? What formula contains the given quantities and the unknown? Wave Speed

18. 17.2 Properties of Mechanical Waves Plan and Solve What unknown are you trying to calculate? What formula contains the given quantities and the unknown? Wave Speed

19. 17.2 Properties of Mechanical Waves Plan and Solve Replace each variable with its known value. Wave Speed

20. 17.2 Properties of Mechanical Waves Plan and Solve Replace each variable with its known value. Wave Speed

21. 17.2 Properties of Mechanical Waves Look Back and Check Is your answer reasonable? Wave Speed

22. 17.2 Properties of Mechanical Waves Look Back and Check Is your answer reasonable? Because the frequency is 3.0 hertz, the wave should travel a distance of 3 wavelengths in 1 second. This distance is 0.75 meters, which agrees with the calculated speed of 0.75 m/s. Wave Speed

23. 17.2 Properties of Mechanical Waves 1. A wave on a rope has a wavelength of 2.0 m and a frequency of 2.0 Hz. What is the speed of the wave? Answer: Wave Speed

24. 17.2 Properties of Mechanical Waves 1. A wave on a rope has a wavelength of 2.0 m and a frequency of 2.0 Hz. What is the speed of the wave? Answer: The speed is 2.0 m × 2.0 Hz = 4.0 m/s Wave Speed

25. 17.2 Properties of Mechanical Waves 2. A motorboat is tied to a dock with its motor running. The spinning propeller makes a surface wave in the water with a frequency of 4 Hz and a wavelength of 0.1 m. What is the speed of the wave? Answer: Wave Speed

26. 17.2 Properties of Mechanical Waves 2. A motorboat is tied to a dock with its motor running. The spinning propeller makes a surface wave in the water with a frequency of 4 Hz and a wavelength of 0.1 m. What is the speed of the wave? Answer: The speed is 0.1 m × 4 Hz = 0.4 m/s Wave Speed

27. 17.2 Properties of Mechanical Waves 3. What is the speed of a wave in a spring if it has a wavelength of 10 cm and a period of 0.2 s? Answer: Wave Speed

28. 17.2 Properties of Mechanical Waves 3. What is the speed of a wave in a spring if it has a wavelength of 10 cm and a period of 0.2 s? Answer: The speed is 10 cm/0.2 s = 50 cm/s (or 0.5 m/s) Wave Speed

29. 17.2 Properties of Mechanical Waves 4. What is the wavelength of an earthquake wave if it has a speed of 5 km/s and a frequency of 10 Hz? Answer: Wave Speed

30. 17.2 Properties of Mechanical Waves 4. What is the wavelength of an earthquake wave if it has a speed of 5 km/s and a frequency of 10 Hz? Answer: speed = wavelength x frequency so wavelength = speed / frequency The wavelength is (5 km/s)/10 Hz = 0.5 km. *Note units: km/s divided by 1/s so (km/s) (s/1) = km Wave Speed

31. 17.2 Properties of Mechanical Waves Amplitude How is the amplitude of a wave related to the wave’s energy? The amplitude of a wave is the maximum displacement of the medium from its rest position.

32. 17.2 Properties of Mechanical Waves The amplitude of a transverse wave is the distance from the rest position to a crest or a trough. It takes more energy to produce a wave with higher crests and deeper troughs. Amplitude

33. 17.2 Properties of Mechanical Waves The more energy a wave has, the greater is its amplitude. Amplitude Rest position High amplitude Low amplitude

34. 17.2 Properties of Mechanical Waves The amplitude of a longitudinal wave is the maximum displacement of a point from its rest position. The more energy the wave has, the more the medium will be compressed or displaced. Amplitude

35. 17.1 Mechanical Waves Wednesday, April 12, 2011 - Opener #7 1. While wading in shallow waters, six waves crash into your legs in a 24-second span. What is the frequency of the waves? 2. CW: Complete and turn in computer wave simulation lab IN BOX. Answers should be on your own paper. CW: Complete all of section 1 and at least start section 2 notes if not done yesterday. CW: PAP 5th & 7th periods - Start and complete NOTES 17.3 and 17.4 abbreviated... Be sure to watch all videos and to do the interactive quick activity with link connection. Earbuds are needed all week. Pizza Party upcoming... HW: PAP - Wave calculations worksheet - side 1 due tomorrow... You can also do side 2 but will be due later... (6th period - side 1 is due Thursday.) CW/HW PAP only: Ch. Review pg. 527-528 #1-24, 29-34 AND pg. 529 #1-6 due Friday. HW PAP: Submit iMovie Project by Friday, April 15th...

36. 17.2 Properties of Mechanical Waves WEDNESDAY, April 13, 2011 - Opener #6 - 5th/7th periods... OPENER: Read through instructions on lab. Record basic objectives and what you are trying to accomplish in lab. CW: Be sure your computer wave simulation lab has been turned IN BOX. CW: Modeling a Transverse Wave with Sand Pendulum... Have out - Handout sheet Side 1 “17.2” #1-5; I’ll pick up and give back tomorrow. CW/HW PAP only: Ch. Review pg. 527-528 #1-24, 29-34 AND pg. 529 #1-6 due Friday. Upcoming Pizza party next week - bring $3.50 - probably Tuesday...

37. 17.2 Properties of Mechanical Waves WEDNESDAY, April 13, 2011 - Opener #6 - 3rd/4th/6th periods... Answer the following. Show formulas and work if applicable. Explain others... 1. While wading in shallow waters, six waves crash into your legs in a 24-second span. What is the frequency of the waves? 2. What is the speed of an earthquake wave if it has a wavelength of 2.3 km and a frequency of 3 Hz? 3.What wave property increases as the energy of a wave increases? CW: Be sure your computer wave simulation lab has been turned IN BOX. 3rd/4th/6th periods CW: Complete all 4 sets of Notes on mechanical waves from podcast page (http://podcast.bryantschools.org/users/dvann)http://podcast.bryantschools.org/users/dvann CW/HW 3rd/4th/6th period - Handout sheet Side 1 “17.2” #1-5 due tomorrow with all work shown including formulas... CW/HW: pg. 471 #1-9 due Friday. Upcoming Pizza party next week - bring $3.50 - probably Tuesday...

38. 17.2 Properties of Mechanical Waves Assessment Questions 1. While wading in shallow waters, six waves crash into your legs in a 24-second span. What is the frequency of the waves? a. 4 Hz b. 18 Hz c. 0.25 Hz d. 2 Hz

39. 17.2 Properties of Mechanical Waves Try answering these Assessment Questions 1. While wading in shallow waters, six waves crash into your legs in a 24-second span. What is the frequency of the waves? a. 4 Hz b. 18 Hz c. 0.25 Hz d. 2 Hz ANS:C frequency = 6 cycles/24 s = 1/4 =.25 cycles/s =.25 Hz

40. 17.2 Properties of Mechanical Waves Assessment Questions 2. What is the speed of an earthquake wave if it has a wavelength of 2.3 km and a frequency of 3 Hz? a. 6.9 km b. 5.3 km c. 6.0 km d. 1.3 km

41. 17.2 Properties of Mechanical Waves Assessment Questions 2. What is the speed of an earthquake wave if it has a wavelength of 2.3 km and a frequency of 3 Hz? a. 6.9 km/s b. 5.3 km/s c. 6.0 km/s d. 1.3 km/s ANS:A from v = freq. x wavelength or v = 2.3 km * 3 cycles/s = 6.9 km/s

42. 17.2 Properties of Mechanical Waves Assessment Questions 3. Which wave property increases as the energy of a wave increases? a. period b. frequency c. wavelength d. amplitude

43. 17.2 Properties of Mechanical Waves Assessment Questions 3. Which wave property increases as the energy of a wave increases? a. period b. frequency c. wavelength d. amplitude ANS:D

44. 17.2 Properties of Mechanical Waves LAB - Sand Pendulum Lab with illustrating waves... Finish essay test if necessary from ch.14-15-16

45. 17.2 Properties of Mechanical Waves FALL 2009 Assignment: 17.1 & 17.2 “DRA” and math problems packet due on Friday. Finish computer lab if you were not done and turn in. Read Section 17.4 and complete notes pg. 514-521 on Sound and hearing. We will only talk about Doppler Effect. You are responsible for reading and taking notes on section 17.4.