Music, Math, and Motion Dr. E.J. Zita The Evergreen St. College

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Music, Math, and MotionDr. E.J. ZitaThe
Evergreen St. College

• Winter week 3
• Friday 23 Jan. 2009

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Ch.11 Waves, continued

• Where to find solutions to 11.a online
• Overview of 11 6, 7, 8, 9
• Jigsaw learning more efficient today, since you
  have already read the sections
• Choose homework together, due next Friday
• Looking ahead

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Where to find Giancoli solutions online
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Review of key derivation from 11.a
F ma -k x - m w2 x k m w2 w2 k/m w
??k/m 2 p f
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Overview of 11 6, 7, 8, 9
11.6 Resonance 11.7 Wave motion 11.8
Transverse Longitudinal waves 11.9 Energy
Transported by waves
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Overview of 11.6 Forced Vibrations Resonance
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Overview of 11.7 Wave motion
Transverse waves
Longitudinal waves
What is the wavelength, frequency, and
amplitude? How are these related to the wave
speed? Do the particles of the medium travel as
the wave travels?
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Overview of 11.8 More on transverse and
longitudinal waves
Note general and specific characteristics of
speeds for each type. Why does a waves break?
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Overview of 11.9 Energy transported by waves
What are the relations between force, energy,
power, and intensity? Must waves occur in a
medium? Must waves transport power? How do
intensity and wave amplitude change with distance
from the source?
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Jigsaw learning-through-discussion

• 1. Count off by 6,7,8,9
• Each team discuss your section
• Identify key points
• Zita will circulate, answering questions
• 2. Mix teams so there is one expert for each
  chapter on each team
• Discuss all sections share your key points
• 3. Whole group gather resolve questions, share
  insights and examples, and choose homework
  together

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More on 11.6 Forced Vibrations Resonance
http//www.youtube.com/watch?vj-zczJXSxnw
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More on 11.7 Wave motion
Transverse waves
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More on 11.8 transverse and longitudinal waves
Speed of TRANSVERSE waves on a plucked guitar
string
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Tension ? Speed of waves
Tension is a force, with units of Newtons
Guess what the speed of acoustic waves in air
depends on?
Now consider plucking a magnetic field line.
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Ch.11.9 Force ? Pressure? Intensity
Pressure Force / Area N/m2
Energy Force distance Intensity Power /
Area Watts/m2 Power Energy/time
rate of energy flow / across a surface
area
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Force ? Energy ? Power
Mechanical energy Work Force
displacement Mechanical energy Kinetic Energy
Potential Energy Kinetic Energy ½ mv2 Potential
energy ability to do work
Units of Energy Force (N) Displacement (m)
Joules Nm
Power rate of doing work Energy / time
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Homework (HW)

• Note Summary (p.315)
• Discuss some Questions (p.316)
• Choose HW (Problems, starting p.317)
• Get as far as you can on every HW problem on your
  own after class
• Then start talking with peers, Zita, Quasr
• Help session here next Thursday at 300
• Do we need another help session Tuesday?
• HW due before class next Friday
• Only NEAT and STAPLED HW will be accepted

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Summary p.315
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Questions
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Looking ahead
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HW Problems
Look at Ch.11 6, 7, 8, 9 together. Together,
choose about 3 problems per section to be due
next Friday.