1. Physics Chapter 5 Section 3
Sounds in strings revisited

3. HW: p 517 #1-5 Do Now: Agenda 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 Length Wavelength
(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!