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 4
• Friday 30 Jan. 2009

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Ch.11 Waves, continued

• Where to find solutions to HW online
• Overview of 11 9, 10, 12, 13
• Discuss sections
• Choose homework together, due next Friday
• Looking ahead

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Giancoli solutions on Moodle
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Review of Ch.11.9 Energy transported by waves
Intensity Power (W) / Area (m2) and Power (W)
Energy (J) / time (s) so Intensity
(is matter transported?
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Overview of 11 10, 11, 12, 13
11.10 Intensity related to amplitude and
frequency 11.11 Reflection and transmission of
waves 11.12 Interference Superposition 11.13
Standing waves Resonance
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Overview of 11.10 Intensity related to
amplitude and frequency
Total energy of simple harmonic oscillator
maximum potential energy E ½ kA2 Where w
??k/m 2 p f, therefore k and E Mass
density volume m r V, volume area
length V S L, and the length is the distance
the wave at velocity v travels in a time t L
v t. Therefore m Substitute this into your
result for E Then Power Energy / time P
E / t Finally, Intensity Power / area I
P/S How does Intensity depend on the Amplitude
and frequency of a wave?
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Overview of 11.11 Reflection Transmission of
waves
Try the PhET workshop on Wave Interference with
ONE DRIP. Explore the similarities between
this wave propagation and that described in
Fig.11-34.a
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Overview of 11.12 Interference and
superposition
Try the PhET workshop on Wave Interference with
TWO DRIPS and a WALL at the far end. Explore
the similarities between this wave propagation
and those described in Figs.11-35 and 11-36
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Overview of 11.13 Standing waves and resonance
How can you find the relationship between the
length L of the string and the wavelength l of
each mode? Look at the 2-drip PhET experiment
with a wall can you detect standing waves?
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Jigsaw learning-through-discussion

• 1. Count off by 10, 11, 12, 13
• 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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Lets try some HW together you choose which
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HW Ch.11-12
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Extra problems
More interesting problems start on p.320
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Hints
67. Dx vt 71. KE1 PI1 KE2 PE2 72. v l
f 77. fn nf1 (ngt1) 79. vmax wA 80 amax
w2A lt g
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Looking ahead
TODAY
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HW Problems
Due not next week, but the following week. Some
people will have midquarter conferences next
Thursday, And everyone will perform Group
Project 1 next Friday.