Upcoming Deadlines

1
Upcoming Deadlines
Pick up a clicker, find the right channel, and
enter Student ID

• Homework 10 Outline for Second Term Paper
• Due Wednesday, April 14th (This Wednesday)
• 10 points (5 points if late)
• Second Term Paper Science Fact or Cinematic
  Fiction?
• Due Wednesday, April 21st (Wednesday of next
  week)
• 100 points (50 points if late)
• There are no more furlough days for this class
  this semester.
• For full schedule, visit course website
• ArtPhysics123.pbworks.com

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Homework Assignment 10

• Outline of your Second Term Paper.
• Topic Science Fact or Cinematic Fiction?

An important component of being a well-educated
adult is the ability to distinguish between fact
and fiction, between science and make-believe.
For this assignment, you will choose a single
physics principle, such as conservation of energy
or the action/reaction principle, and describe
three scenes from three different films that
incorrectly illustrate that physics law or
principle.
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Homework Assignment 10

• For example, you can describe how the
  action/reaction principle is violated during a
  fight sequence when one character recoils but
  without a matching reaction on the other
  character.
• The three films you select can be animated or
  live-action featuring CGI animation special
  effects.
• You are strongly encouraged to find three scenes
  that are as different as possible from each other
  yet have the same fundamental error in the
  physics.

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Homework Assignment 10

• Post your outline in a blog entry entitled,
  Outline for the Second Term Paper.
• Outline due by 8am on Wednesday, April 14th.
• 10 points (if late, 5 points)
• The term paper itself is due a week later.
• Length, structure, grading rubric, etc. are
  similar to the first term paper.

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Extra Credit Opportunity
Visit the Walt Disney Family Museum

• Give me your ticket receipt for ten points extra
  credit.

Hours Wednesday-Monday 10a.m.-6p.m Admission
15.00 for students Location 104 Montgomery
Street Inside The Presidio of San Francisco
Special Exhibition April 7 - June 2010 Walt
Disney's Peter Pan
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Extra Credit Opportunity
Visit the Exploratorium in San Francisco.

• Give me your ticket receipt for ten points extra
  credit.

Hours Tuesday-Sunday 10a.m.-5p.m Admission
11.00 for students Location 3601 Lyon Street,
SF 94123 Next to Palace of Fine Arts complex
www.exploratorium.edu
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Extra Credit Opportunity
Complete anonymous online survey by April 15th
five points extra credit.

• Survey Questions
• What do you like most about the course?
• What do you dislike most about the course?
• What changes would you suggest?
• Do you have any other comments?

Go to course website for link to survey. After
completing survey, follow the instructions to
receive extra credit.
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Activating your Clicker

• Turn on your clicker.
• Enter the channel number or letter for joining
  this class. Hit Enter/Send key.
• Clicker should read AP123S258
• Type in your student ID hit Enter/Send.
• Clicker is now ready to use leave it on.

Hit any key to wake the clicker from sleep mode.
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Survey Question

• How many times have you visited the Disney museum
  in San Francisco?
• Never been
• Visited once
• Visited twice
• Been more than twice

10
Wave Relations

• Wave speed, wavelength frequency related.
• (Wave speed) (Wavelength) x (Frequency)

For a given wave speed, short waves have fast
oscillations and long waves have slow
oscillations. Note Hertz means oscillations
per second so 100 Hertz 100 oscillations per
second
11
Waves by the Shore

• Water waves move past a wooden post with a speed
  of 6 feet per second and wavelength of 2 feet.
• What is the frequency of the oscillations of the
  waves at the dock post?

• 12 Hertz B) 3 Hertz C) 2 Hertz
• D) 1/2 Hertz E) 1/3 Hertz

6 ft/s
2 ft
2 m
6 m/s
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Waves by the Shore
B) 3 Hertz (Speed) (Wavelength)x(Frequency) (
6) (2) x (3) The frequency of the waves is 3
Hertz,or 3 oscillations per second, so each
oscillation takes 1/3 second.
6 ft/s
2 ft
2 m
6 m/s
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Demo Helium Voice
Breath Helium

• Wavelength of sound is unchanged (size of vocal
  cords is unchanged).
• Frequency of voice is higher.

He
(Wave speed)
Talk like me!
(Frequency)
(Wavelength)
This means that the wave speed (speed of sound)
is higher in helium, True or False?
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Demo Helium Voice
Breath Helium

• True.
• Helium atoms are much lighter than air molecules
  so they travel much faster than air molecules.
• The faster Helium atoms transport sound at a
  higher speed than air molecules.

He
Talk like me!
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Waves SoundPart II
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Talkies
The first feature film with synchronized sound,
1927s The Jazz Singer, was made using Vitaphone,
a sound-on-disc technology. Sound-on-film,
however, would soon become the standard for
talkies by the early 1930s.
Sound-on-film sound track
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Silly Symphonies
The Skeleton Dance (1929)
From 1929 to 1939, Disney studios created 75
cartoons in the Silly Symphonies series, starting
with The Skeleton Dance. This series dominated
the Oscars, winning yearly from 1932 to 1937.
http//www.youtube.com/watch?vjkhxjzc9uuE
Silly Symphonies had many imitators, including
Warner Bros.s Looney Tunes and Merrie Melodies,
as well as MGM's Happy Harmonies.
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South Park Bigger, Longer Uncut (1999)
Disney (and the rest of the industry) believed
that audiences would not sit through a
feature-length animated feature with simplistic
animation.
South Park proved him wrong, making over 82
million worldwide, with a 21 million budget. Was
it the catchy music?
http//www.youtube.com/watch?v6UMaTg3lSf4
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Frequency Pitch
Musical notes are sound waves of different
frequencies.
The faster vibrations, have higher frequency.
Higher frequencies results in higher pitch for
the musical note.
20
Standing Waves

• When a wave interferes with its reflection, this
  may create a standing wave.

21
Fundamental Overtones
The Fundamental is the lowest frequency standing
wave. The Overtones are twice, three times, etc.,
the frequency of the Fundamental.
110 Hz (A2)
220 Hz (A3)
330 Hz (E4)
Frequencies of standing waves for a 6 foot long
organ pipe
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Octave

• The note produced by two strings, one half the
  length of the other, sounded similar.
• In Western music these two notes are said to be
  an octave apart.
• Higher note is twice the frequency of the lower.

Men and women typically sing an octave apart.
C5 C4
Sing Some-where over the rainbow
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Perfect Fifth

• If the second string is 2/3rd the length then the
  two notes are said to be a fifth apart.
• Higher note has 50 higher frequency.

Separation between tenor and bass or soprano and
alto.
G4 C4
Sing Twin-kle, twin-kle little star
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Strings and Pipes
Shorter the string or the pipe, the higher the
frequency of the note thats produced.
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Brass Instruments
Resonant standing waves produced in a pipe
(horn) the set of frequencies (notes) depends on
the length of the pipe.
Valves used to vary the length through in pipe
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Woodwind Instruments
Resonant standing waves also produced in a pipe
but the pipe length varied by air holes
(finger-holes, keys, or pads).
Flute
Oboe
Cor anglais
Saxophone
Clarinet
Bassoon
Meter stick
27
Demo Playing a Straw

• Can make a simple reed by cutting a straw, as
  shown, lightly placing it between your lips, and
  blowing hard.

What happens if you shorten the straw (e.g., cut
it in half)?
28
Demo Hoot Tubes

• Large tube has a metal screen near one end.
• Heat screen with a flame.
• Remove tube from the flame and it plays like an
  organ pipe.

The sound created by the larger hoot tube has a
larger A) Frequency B) Wavelength C)
Amplitude
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Hoot Tubes, Analyzed

• C) Amplitude.
• Remove the flame and hot air rises from the
  screen, drawing in cold air.
• Hot air rising through pipe causes vibration at
  natural frequency, which depends on the length of
  the pipe.
• Amplitude depends on the diameter of the pipe.

FLAME
30
Natural Frequencies

• Metal baseball bat and wooden bat sound very
  different when dropped to the floor.
• Different materials and shapes vibrate at their
  own natural frequencies.

31
Forced Vibrations

• Vibrating guitar strings force the vibration of
  the guitars body, producing the sound.

731 Hz
553 Hz
Circular rings indicate where the surface
vibrates up and down
32
Demo Tuning Fork Sound Box

• Tuning fork by itself is not very loud.
• Sound is much louder if it is held against a
  sound box, such as the body of a guitar or any
  similar rigid surface.
• The tuning fork forces the surface into
  oscillation at the same frequency.

33
Resonance

• Resonance occurs when forced vibrations match an
  objects natural frequency.
• Oscillations grow in amplitude due to
  synchronized transfer of energy into the
  vibrating object.

34
Acoustic Resonance
If the amplitude of the sound is sufficiently
large, resonant vibrations can shatter a wine
glass. This may be achieved by
exceptionally powerful singers (and by average
singers using electronic amplifiers).
http//www.youtube.com/watch?vBE827gwnnk4
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Tacoma Narrows Bridge

• In 1940, the first Tacoma Narrows bridge was
  destroyed by resonance.

First Bridge
Second Bridge
Wind-forced oscillations that happened to match
one of the bridges natural frequencies.
36
Tacoma Narrows Bridge
First Bridge
Second Bridge
http//www.youtube.com/watch?vj-zczJXSxnw
37
Wave Spectrum

• To appreciate what it takes to create a realistic
  animation of water, such as the ocean, its
  useful to understand the concept of wave spectrum.

Real
CGI
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The Abyss (1989)
James Camerons The Abyss won an Oscar for Best
Visual Effects, thanks to ILMs creation of the
first CGI character made of water.
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The Old Man and the Sea (1999)
Aleksandr Petrov, the paint-on-glass animator,
creates a realistic ocean with a full spectrum of
waves, from major surges to minor ripples.
http//www.youtube.com/watch?vl2_KszEnlq0
40
Spectral Decomposition
Amplitude
A complicated wave pattern may be decomposed as a
sum of simple waves. The graph of intensity (or
power) versus frequency is the spectral
decomposition.
Time
Decomposition into waves
Intensity
Frequency
41
Class Demo Wave Spectrum
42
Timbre and Spectrum

• A musical instrument playing a single note
  produces not just that notes frequency but
  others as well, mostly overtones.

The frequencies produced by a flute playing an A
(slightly flat) show that the fundamental (436
Hz) and the harmonic (872 Hz) have almost the
same amplitude. The spectrum of a tuning fork
has (mostly) a single peak at the fundamental.
43
Why Instruments Differ

• The unique spectrum of frequencies for a musical
  instrument gives that instrument a unique
  signature, which is called the instruments
  timbre (or quality).

Playing this note (196 Hz)
44
Ocean Wave Spectrum
As the wind speed increases, the intensity of the
large surge waves increases dramatically while
the short ripples increases much less.
High Winds
Intensity
LowWinds
Low Frequency Long Wavelength
High Frequency Short Wavelength
45
Timber of a Material
Spectrum of waves will be different for different
materials due to density, viscosity, surface
tension, depth of the fluid, etc.
Gushing Oil Well
Jello waves
http//www.youtube.com/watch?vpDyqhOL1ePU
46
Media That Transmit Sound
Sound travels better through elastic liquids and
solids, such as water and rocks, than through
air. This is due to the close proximity of the
atoms as they vibrate.
Sonar used by whale and dolphins
47
Demo Tin-can Telephone

• Vibrations in a material transmit waves, such as
  when sound is communicated along the string of in
  a tin can telephone.

48
Demo Wave Spectrum

• Strike the iron grate and listen to the sound.
• Next, loop the string loop on your finger and let
  the iron grate hang freely.
• Place your fingertips in your ears.
• Strike the iron grate again and listen to the
  difference in the sound.

Hear richer, louder sound transmitted by string
49
Demo What Your Voice Sounds Like

• Your voice sounds different to you when you hear
  it from a recording.
• This is because when you are speaking aloud, most
  sound waves reach your ear traveling through the
  solid flesh and bone of your skull.

Leave yourself a voice-mail
50
Oil on the Water
Exxon Valdez accident
Wave spectrum changes due to oil slick
51
Shallow Water Waves
As waves enter shallow water, they slow down,
grow taller and change shape.
From www.seafriends.org.nz
52
Approaching Shore
As waves enter shallow water, they slow, grow
taller and change shape. At a depth of half its
wave length, the rounded waves start to rise and
their crests become shorter while their troughs
lengthen.
Although their period (frequency) stays the same,
the waves slow down and their overall wave length
shortens.
From www.seafriends.org.nz
53
Wave Bending
Beach
When wave fronts approach a gently sloping beach
on an angle, they slow down in the shallows,
causing them to bend towards the beach. If the
beach slopes gently enough, all breakers will
eventually line up parallel to the beach.
54
Surf Zone
The waves steepen and finally break in the surf
when depth becomes less than 1.3 times their
height. Waves change shape in depths depending
on their wave length, but break in shallows
relating to their height!
From www.seafriends.org.nz
55
Breakers
Spilling breakers are arise from long waves
breaking on gently sloping beaches. There are
several rows of breakers.
Plunging breakers can occur on moderate sloping
beaches. There is only one row of breakers.
Surging breakers surge over steeply sloping (but
not vertical) beaches or rocks. Waves break one
at a time.
From www.seafriends.org.nz
56
Clash of the Titans (1981)
Notice how fake the waves looks because the
spectrum and the timing are wrong.
http//www.youtube.com/watch?vJgiOx1fQzoA
Tidal wave scenes were created with scale models.
57
Tsunami Waves

• Tsunamis are ordinary water waves, just like
  waves in your bathtub, but because they are
  typically generated by deep sea earthquakes they
  carry huge amounts of energy and momentum,
  traveling at almost 500 mph while in the deep
  ocean.

The tsunami of 26 December 26th 2004 was produced
by an earthquake whose epicenter was located off
the coast of Indonesia in the Indian Ocean. The
death toll is estimated at over a quarter of a
million persons.
Animation by Vasily V. Titov
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2012 (2009)
Because the tidal waves are so massive they dont
break but rather surge over obstacles.
http//www.youtube.com/watch?v_6G3Nr0Lrlo
Using CG allows greater control of timing and
shapes.
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Next LectureEffects AnimationHot Cold

• Homework 10 (Outline of 2nd Term Paper)
• Due Wednesday, April 14th (This week)

Please return the clickers!