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Physics Chapter 5 Section 3 Sounds in strings revisited.

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Presentation on theme: "Physics Chapter 5 Section 3 Sounds in strings revisited."— Presentation transcript:

1 Physics Chapter 5 Section 3 Sounds in strings revisited

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3 HW: p 517 #1-5  Learning Objective  Explain direct and inverse relationships  Explain how wave speed, wavelength, and frequency are related  Create a data table to organize data for experiments.  Success Criteria  Describe what determines wavelength and sound  Describe the relationship between tension and speed of a wave  Describe the relationship between wavelength and frequency  Determine the velocity of a wave using the equation  Calculate wavelength of a standing wave  Describe how the pitch of the sound produced by a vibrating string depends on the wave speed, wavelength and frequency of the waves on the string.  Do Now:  Write LO and SC on new left page  WDYS/WDYT on page 508  Agenda  Do Now  Investigation 5.3  Summary/Exit Ticket

4 Investigate 5.3 (Guidelines for 1-7)  Same set-up as Investigation 1  What kind of wave is the string making?  How do you calculate wavelength?  Standing Wave - this is similar to the waves made in the spring  The wavelength is twice the length of the string

5 Sample Data Table String LengthWavelength (2x string length) Pitch (high, low, or medium)

6 Investigation 5.3 (Guidelines for 8-12)  Complete with your group  Remember that speed is distance traveled over a period of time.

7 Summary/Exit Ticket  How does changing the wavelength effect the velocity?  How does changing the frequency effect the velocity?

8 HW: p 517 #1-5  Learning Objective  Explain direct and inverse relationships  Explain how wave speed, wavelength, and frequency are related  Create a data table to organize data for experiments.  Success Criteria  Describe what determines wavelength and sound  Describe the relationship between tension and speed of a wave  Describe the relationship between wavelength and frequency  Determine the velocity of a wave using the equation  Calculate wavelength of a standing wave  Describe how the pitch of the sound produced by a vibrating string depends on the wave speed, wavelength and frequency of the waves on the string.  Do Now:  If you keep the wavelength the same, how can you change the velocity of the wave?  Agenda  Do Now  Notes 5.3  Summary/Exit Ticket

9 Physics Talk 5.3  What kind of wave does the vibrating string produce?  How do you calculate the wavelength?  A standing wave  The wavelenght is twice the length of the string

10 Physics Talk 5.3  How does frequency relate to pitch?  Equation for wave speed  The higher the frequency, the higher the pitch  Wave speed = wave frequency x wavelength

11 Physics Talk 5.3  How do we solve for frequency?  Rearrange the equation to read

12 Physics Talk 5.3  What happened when you shortened the length of the string?  How is this shown in the equation?  The wavelength was shortened  Pitch increased  Frequency increased  Dividing by a smaller number on the bottom, gives us a larger frequency  If you have to share something with fewer people, you get more

13 Physics Talk 5.3  What kind of mathematical relationship does this show?  What is an inverse relationship?  Inverse Relationship  A relationship where when one value increases, the other decreases, or as one value decreases, the other increases

14 Physics Talk 5.3  How is frequency an example of an inverse relationship?  Decreasing the wavelength increases the frequency

15 Physics Talk 5.3  How are tension and pitch related?  Since the wavelength did not change, and the frequency increased, this means the wave speed increased  An increase in tension, produces a larger force, which leads to a larger acceleration on the string (F=ma)

16 Physics Talk 5.3  How are tension and pitch related? (continued)  When the force accelerates the string, the wave speed increases and the string vibrates faster  Since the wave is faster, the frequency must also be faster, leading to a higher pitch

17 Physics Talk 5.3  What is a direct relationship?  Example of direct relationship  A relationship where as one value increases, the other value also increases  Increasing the wave speed also increases the frequency and pitch

18 Physics Talk 5.3  How does increasing the thickness of the string lead to a different pitch?  When the string is larger, it has a greater mass for the wave to travel through  This also means it takes more force to stop the string from vibrating  The force is the tension in the string

19 Physics Talk 5.3  How does increasing the thickness of the string lead to a different pitch?  Since the mass is heavier, the acceleration will be less (F=ma)  This creates a slower wave speed  Decreasing wave speed will decrease the frequency and pitch

20 Physics Talk 5.3  When do standing waves occur?  How does string length related to standing waves?  When the length of the coiled spring or string has a certain relationship  The length much be 1/2, 1, 3/2, 2, etc of the wavelength

21 Physics Talk 5.3  Equation for standing waves  Standing waves occur when the the following equation is met: L = string length n = a whole number (1, 2, 3, etc) Lambda = wavelength

22 Physics Talk 5.3  How do you calculate the period for a wave?  How is a period related to the frequency?  T is the period  The frequency is the reciprocal of the period

23 Sample Problems 1 and 2  p 513  Use GUTS  When in doubt, draw it out  Pictures are very helpful!

24 What do you think now?  Why does the pitch change when you change the tension in the string? USE PHYSICS!


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