Upcoming Deadlines

1
Upcoming Deadlines

• Tenth Homework (Outline of Second Paper)
• Due Wednesday, November 4th (Next week)
• Veteran's Day (Campus Closed)
• Wednesday, November 11th (No homework due)
• Second Term Paper
• Wednesday, November 25th
• (Day before Thanksgiving no class that day)
• For full schedule, visit course website
• ArtPhysics123.pbworks.com

2
Extra Credit Opportunity
Complete anonymous online survey by October 30th
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.
3
Extra Credit Opportunity
Complete anonymous online survey by October 30th
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?

Opportunity Ends This Friday!
Go to course website for link to survey. After
completing survey, follow the instructions to
receive extra credit.
4
Homework Assignment 10

• Outline of your Second Term Paper.
• Topic Science Fact or Cinematic Fiction?
• For this assignment, you will select an animation
  film (or a live-action film featuring CGI
  animation special effects) and critique the
  elements in one scene that are physically
  unrealistic.
• For example, you can describe how the
  action/reaction principle is violated during a
  fight sequence, such as when one character
  recoils but without a matching reaction on the
  other character.

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Homework Assignment 10

• Your analysis must describe at least three
  distinct physical principles that are incorrect
  in your selected scene.
• Alternatively, you may choose a single physics
  principle, such as conservation of energy, and
  describe three scenes (possibly from different
  films) that incorrectly illustrate that
  principle.
• Post your outline in a blog entry entitled,
  Outline for the Second Term Paper.
• Outline due by 8am on Wednesday, November 4th.
• 10 points (if late, 5 points)

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Effects AnimationPart I Waves
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Effects Animation

• Animation generally divided into two categories
  Character and Effects.

Character animation for Alex the Lion
Effects animation for the Ocean
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Waves

• Today well look at topics in effects animation
  that are related to the phenomena of waves.

String
Sound
Water waves
Light waves
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Transverse Waves

• For transverse waves the waves amplitude is
  perpendicular to the waves motion.

Amplitude
Wave Motion
Amplitude
10
Flag Cycle

• Flag cycle is a common effects animation exercise
  for learning waves.

Play
Ripples in cloth are transverse waves.
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Luxo Jr. (1986)
Pixars first film, Luxo Jr., was created to
demonstrate that realistic lighting could be
achieved in computer animation.
Luxo Jr.s cord shows some nice transverse waves.
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Demo Torsional Wave Machine
Torsional wave machine creates slow transverse
waves that are easily visible.
13
Doing The Wave

• Synchronized standing and sitting by a stadiums
  crowd is an example of a transverse wave.

Video analysis indicates that it takes only a few
dozen fans leaping to their feet with their arms
up to trigger a wave. Once started, it usually
rolls in a clockwise direction at a rate of about
40 feet per second, or about 20 seats per second.
At any given time, the wave pulse is about 15
seats wide.
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Longitudinal Waves

• For longitudinal waves, amplitude and wave motion
  are parallel.

Wave Motion
Amplitude
Amplitude
A crowd can do a longitudinal wave by moving
side-to-side instead of up-and-down
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Nature of Sound in Air

• Sound in air is a longitudinal wave created by
  compressions and rarefactions.

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Demo Sound is not Wind

• With sound, air molecules oscillate in place.
• With wind, air moves from place to place.

Smoke rings are not sound because the air moves
from place to place.
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Wavelength

• Wavelength is distance between crests or between
  troughs of waves.

Longitudinal
Transverse
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Frequency

• Number of oscillations per second is the
  frequency of a wave.

Wave frequency depends on how quickly you shake
your hand.
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Wave Speed

• The speed at which waves travel is called the
  wave speed.
• Speed of sound 725 miles per hour
• Speed of light 186,000 miles per hour

Water waves at the beach move a few miles per
hour
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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
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Wave Simulator (Water)
Visualize water waves using a computer simulation.
From phet.colorado.edu
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Waves by the Shore

• Water waves move past a wooden post with a speed
  of 6 feet per second and wavelength of 2 feet.
• How much time does it take for the water by the
  post to rise and fall once?

• 12 seconds B) 3 seconds C) 2 seconds
• D) 1/2 second E) 1/3 second

6 ft/s
Period?
2 ft
2 m
6 m/s
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Waves by the Shore
E) 1/3 second (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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Beach Waves
As waves enter shallow water, they slow down,
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
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Surf Zone
The 'bumps' gradually steepen and finally break
in the surf when depth becomes less than 1.3
times their height. Note that waves change
shape in depths depending on their wave length,
but break in shallows relating to their height!
From www.seafriends.org.nz
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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
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Wave Bending
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.
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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
29
Wave Simulator (Sound)
Visualize sound waves using a computer simulation.
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Demo Hearing Sound

• Range of human hearing is roughly 20 Hertz to
  20,000 Hertz.
• Wave speed for sound is 330 m/s
• Wavelength of 20 Hertz is 16 m (about 50 ft)
• Wavelength of 20,000 Hz is 1.6 cm (½ inch)

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Hearing by Age Sex
Poor Hearing
GoodHearing
Hearing acuity decreases with age, especially in
the high frequencies. In general, women have
greater acoustic sensitivity than men.
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Hearing in Animals
Frequency range varies widely, depending on
natural adaptation using sound to communicate,
locate food, avoid predators, etc.
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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!
35
Demo Make Some Noise

• Lets experience the loudness of sound like by
  clapping at various decibel levels.

Sound Meter
Start clapping softly and slowly increase or
decrease loudness, as I direct you using the
sound meter.
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Doppler Effect

• Sound coming from a moving object has a different
  wavelength and frequency than if it were
  stationary.
• If moving towards you, wavelength shorter and
  frequency higher.
• If moving away, wavelength longer and frequency
  lower.

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Demo Doppler Shift

• Hear frequency as higher when buzzer is moving
  towards you and hear it as lower when moving away
  from you.

Shorter Wavelength
Higher Frequency
Lower Frequency
Longer Wavelength
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Doppler Effect and Shocks
When the source travels at or above the speed of
sound (Mach 1 or more), the wavelength goes to
zero and a shock wave is formed.
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Sonic Boom
A intense shock wave is formed when a plane
travels faster than the speed of sound (765 mph).
F/A-18 Hornet passing through the sound barrier
Play
Loudness of a sonic boom is about 130-135
decibels.
40
Cracking the Whip
The tip of a whip goes faster and faster, taking
much of the energy from the rest of the whip, and
can reach supersonic speed, creating a sonic boom
at the snap.
41
Combustion
Two types of combustion, classified by their
speed
Deflagration Rate of combustion slower than the
speed of sound. Most combustion is deflagration.
Detonation Rate of combustion is faster than the
speed of sound. Only with high explosives.
Candle
Atomic Bomb
Firecracker
Dynamite
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Combustion Waves
Deflagration wave
Burn
Sound
Burn
Detonation wave (Blast shock wave)
Sound
Trinity Atomic Test
43
Demo Flaming Pumpkin
Cloud of corn starch combusts rapidly due to the
large amount of oxygen available to each
grain. Example of a rapid deflagration.
Blow
44
Demo Flaming Pumpkin
45
Coal Dust Explosions
Coal dust is extremely volatile and highly
explosive.
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Animation of Dust Explosions
The expanding fireball of an explosion is another
example of effects animation.
A side-by-side comparison of effects animation
with a photograph of a staged coal-dust explosion.
From Animating Suspended Particle Explosions, B.
Feldman, J. OBrien, O. Arikan, UC Berkeley,
SIGGRAPH 2003
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Next LectureEffects AnimationPart II

• Homework 10 (Outline of 2nd Term Paper)
• Due Wednesday, November 4th

Please return the clickers!