Transcript Uniform Motion - artphysics123

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Fifth Homework (Video Analysis of a Path of Action)
Due Tuesday, February 21st (Next week)
15 points (10 points if late)
Sixth Homework (Stop-motion Animation of Falling)
Due Tuesday, February 28th (In two weeks)
20 points (if late, 10 points)
Bonus prize of 20 extra points to top three.
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exhibition at the San
Jose Museum of Art.
Exhibition opens on
February 3rd
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visit (ticket receipt or
photos) for 5 points
extra credit.
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Extra Credit Opportunity
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Short Films
Opens 2/10/2012 at
Camera 3 Downtown
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for 5 points extra credit.
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event in downtown San Jose.
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Conference) event in San Francisco.
Turn in proof of your attendance (e.g., access pass,
ticket receipt) for 10 points extra credit.
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Art of Dreamworks’ Puss in Boots at the
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Homework Assignment #5
In this assignment you’ll again use Tracker
software to analyze the motion of a moving
object from video reference.
First, shoot some reference of yourself doing a
running jump.
Position your camera so that you're in frame the
entire time that you're in the air.
Stage the jump to be in profile.
Shoot at least 5 takes, even if they are more or
less the same.
Homework Assignment #5
Original Video Reference
Homework Assignment #5
Import your video reference into the Tracker
software (as in previous homework).
Track the center of your waistline or beltline,
which is approximately the location of your
center of gravity.
Marking your position from the time you leave the
ground until you’ve landed.
After tracking your motion, upload the screen
image from Tracker to your blog into a post
called "Video analysis of path of action".
Homework Assignment #5
Straight Line
Parabolic
Path of Action
Parabolic Curve
Homework Assignment #5
Finally, rewind your video to the first frame of
your jump and from the "File" menu select
"Record -> Quicktime Movie".
Hit the play button and allow the clip to play
until the end of your jump. Next, in the
"Capturing Quicktime MOV" window click
"Save As" to save the recording.
Homework Assignment #5
Video Reference with Tracking
Homework Assignment #5
Check that your saved Quicktime movie has the
track showing the path of action then put both
clips (original and with tracking) in your blog
post using YouTube or Vimeo.
This assignment is due by 8am on
Tuesday, Feb. 21st (week from today).
15 points (10 points if late)
Assignment Checklist
* Video clip has you running and jumping at least five times.
* On one of the jumps you track the center of your body while
you're in the air.
* Show plots for both horizontal (x) position versus time and vertical
(y) position versus time.
* Graph of horizontal position versus time is roughly a straight line.
* Graph of vertical position versus time is roughly a parabolic arc.
* Post your screen shot in a blog entry entitled "Video analysis of
path of action".
* Post your original reference clip of your five jumps.
* Also post a recorded Quicktime movie showing your path of
action for one jump.
Activating your Clicker
* Turn on your clicker.
* Enter the channel number or letter for joining
this class. Hit Enter/Send key.
* Clicker should read AP123S1
* Type in your student ID; hit Enter/Send.
Clicker is now ready to use.
Hit any key to wake
the clicker from sleep
mode.
Survey Question
How easy have you found it to
use the Tracker software?
A) Pretty easy to use
B) A little confusing but OK
C) Frustrating to use
D) Haven’t tried using it yet
Note: You score 1 point of credit for answering
survey questions, regardless of your answer.
Review Question
When a trebuchet throws a
stone at what angle should
it be released in order to
get maximum range?
A) Zero degrees (straight)
B) 30 degrees
C) 45 degrees
D) 60 degrees
E) 69.5 degrees
Releasing the Projectile
The release mechanism
is designed to throw
the rock at a 45
degree angle.
45º
Release
Maximum Range
Maximum range is at a launch angle of 45
degrees (when air resistance is negligible).
Height
Same initial speeds
Range
Review Question
The motion graph for a ball drop,
going from the apex until the ball just
touches the ground, looks like:
A)
B)
C)
D)
Motion Graph of a Ball Drop
Height
D)
Frames
Arcs in Animation
Disney’s Principles of Animation
In their classic book, Disney Animation –
The Illusion of Life, Frank Thomas and
Olie Johnston list a set of basic
principles for animation.
1.
2.
3.
4.
5.
Squash & Stretch
Timing
Anticipation
Staging
Follow Through
& Overlapping Action
6. Straight Ahead &
Pose-to-Pose Action
7. Slow In and Slow Out
8. Arcs
9. Exaggeration
10.Secondary Action
11. Appeal
Disney’s Principles of Animation
In their classic book, Disney Animation –
The Illusion
of Life,already
Frank Thomas
and
We have
discussed
Olie Johnston
listofa these
set of basic
several
principles of
principles
for animation.
animation,
specifically:
1.
2.
3.
4.
5.
Squash & Stretch
Timing
Anticipation
Staging
Follow Through
& Overlapping Action
6. Straight Ahead &
Pose-to-Pose Action
7. Slow In and Slow Out
8. Arcs
9. Exaggeration
10.Secondary Action
11. Appeal
Disney’s Principles of Animation
In their classic book, Disney Animation –
The Illusion
of Life,
Frank
Thomas
and
Today
we will
discuss
arcs
Olie Johnston
list athey
set of
basicto
and how
relate
principles
for animation.
animated
motion.
1.
2.
3.
4.
5.
Squash & Stretch
Timing
Anticipation
Staging
Follow Through
& Overlapping Action
6. Straight Ahead &
Pose-to-Pose Action
7. Slow In and Slow Out
8. Arcs
9. Exaggeration
10.Secondary Action
11. Appeal
Arcs of Motion
Motion usually follows an
arc, which may be simple,
like a circle, or very
complex and irregular.
Importance of Arcs
Disney animation legends Frank
Thomas and Olie Johnston write:
One of the major problems
for the inbetweeners is that it
is much more difficult to
make a drawing on an arc.
Right
Drawings made as straight
inbetweens completely kill
the essence of the action.
Wrong
Circular Arcs
Circular arcs are common since
motion is often around a fixed
pivot point, such as a joint.
Speed in Circular Motion
Rotational Speed: Revolutions per second
Tangential Speed: Total distance per second
Same Rotational Speed
Different Tangential Speeds
Rolling & Slipping
1
2
3
4
5
6
7
ROLLING
Rolling ball turns one revolution when it
travels a distance equal to three times its
diameter (actually 3.1416 diameter)
1
2
3
4
5
SLIPPING
Slipping and rolling are both uniform in spacing and rotation.
Throwing Arm
The longer the
throwing arm, the
greater the
tangential speed
so the farther it
can throw.
Sling lengthens the
arm at almost no
cost in the weight.
Doubling the speed
quadruples the range!
Timing on Circular Arcs
A circular arc is a simple path of action but the
timing may be complex and textured.
In this golf swing the
motion:
• Slows out (accelerates)
to hit the ball
• Uniform after the hit
• Slows in as the swing
finishes follow-through
Non-Uniform Circular Motion
Two common types of motion on circular arcs that
have non-uniform timing and spacing are:
Exponential Spacing
Example:
Tipping over
Pendulum Spacing
Example:
Stride in
walking
Tipping Over
Tipping over is a common example of motion
on a circular arc. Two ways to tip over:
X
Center tipped past
point of contact
Center past an edge
Tipping Rotation
A brick rotates about a point as it tips;
that point is the center of a circular arc.
X
Friction tends to keep the brick from sliding until it
loses contact with the table.
Exponential Spacing
Release
1
1
Constant acceleration (Odd Rule)
3
2
5
3
7
1
Release
4
2
3
Exponential Spacing
4
As the slope of the incline increases,
the acceleration itself accelerates.
Rolling off a Tipping Point
1 2 3 4
5
6
7
Peak
8
Slowing out from a tipping point is very slow
initially, but then accelerates rapidly.
Video Reference of Tipping Brick
http://www.youtube.com/watch?v=otYAYMZ4iGg
Anticipation & Exponential Spacing
Texture of the
timing as the brick
tips over creates
anticipation, which
you want at the start
of a scene
Also notice motion
blur near top of
brick, which has
large tangential
speed.
Pendulum Spacing
A pendulum’s path of action is also a circular
arc but the spacing is very different from the
exponential spacing of tipping over.
Spacing & Timing in Swinging
A pendulum will slow in and out as it
swings back and forth, the same as a
ball rolling in a half-pipe.
Most of the texture in the timing is at the
endpoints; the timing is even in the center.
Pencil Test Example
http://www.youtube.com/watch?v=xuoJdNGxffU
Motion Graph for Pendulum
The motion graph (angle vs. frame)
shows that the timing is mostly textured
(curves the most) at the apexes.
#7
Angle
#1
#4
Ball goes fastest around the
bottom but the speed is
almost constant.
Frame
Uniform Rotation in Perspective
The timing for uniform rotation has
texture when seen in perspective.
Half orbit
Quarter
orbit
Rotation from key #1 to #5 in background takes
twice as long as from #6 to #8 in foreground.
Swinging in Perspective
Visually the timing
has even more
texture when the
swing occurs in
perspective.
Demo: Don’t Flinch
Pendulum swings back and forth yet it
doesn’t hit your face.
Bowling Ball Pendulum
http://www.youtube.com/watch?v=UNsD15GjWWE
Click
This video clip lets you
experience what it’s like
to do this demo.
Demo: Interrupted Pendulum
An “interrupt” bar changes the
radius of the arc for a pendulum.
Tangential speed
does not increase
due to the pendulum
whipping around the
interrupt bar.
Energy is not
increased by the
interrupt bar so ball
swings back to the
same spot.
Bar
How Does the Brick Fall?
Does the brick rotate
and then fall down
the side of the table?
1
2
3
No! The brick does not
4
fall this way.
X
Video Reference of Tipping Brick
http://www.youtube.com/watch?v=otYAYMZ4iGg
Forces on the Tipping Brick
The table pushes on the
brick upward and
towards the right.
Gravity pulls downward
Center of the brick shifts down
and towards the right.
If no table…
Pushing Off by the Table
The table pushes away
on the brick, which
causes the brick to
move away from the
table as it falls.
Once it loses contact
with the table, only the
force of gravity
accelerates the brick.
Centrifugal Force
Insect inside a can rotating in a circle
When we move on an
arc, it seems to us as
if there is an outward
force, pushing us
away from the center
of the circle.
Physicists call this
apparent force the
centrifugal force.
What we see
What the
insect feels
Class Demo: Bucket Overhead
I will put a bucket full of water
over my head without getting
wet. How?
By rotating it fast enough.
The water stays in the bucked
as if pressed into it by a
centrifugal force.
You experience
centrifugal force on
taking a sharp turn
Centrifugal
Force
Wile E. Coyote & Loop-D-Loop
Watch carefully as Wile E. Coyote travels in a
circle around a natural arch bridge.
From “Beep Beep” (1952)
http://www.youtube.com/watch?v=p4YxdXw9evc
Wile E. Coyote & Loop-D-Loop
If you go fast enough then it is
possible to travel upside-down,
as Wile E. Coyote does in this
scene. True or False?
“Beep Beep” (1952)
Wile E. Coyote & Loop-D-Loop
True.
If his speed is high enough then he stays
in contact with the arch, just like the
water in the spinning bucket.
Demo: Loop-the-Loop
If the speed of
the ball is large
then not only
does it stay on
the track, the
ball even pushes
outward and
against the rail.
Release
Velocity
Demo: Loop-the-Loop
Ball could even
circle a loop with
a gap, if the
speed was just
right so gravity
was equal to the
centrifugal force.
Release
Velocity
GAP
Jackass 2 (2006)
http://www.youtube.com/watch?v=36fD7KSUjkw
Simulated Gravity
Centrifugal force could be
used to simulate gravity in
a space station.
With the appropriate
rotational speed a person
on the outer rim would feel
as if they stood on the
surface of Earth.
Scientifically accurate in the
movie 2001: A Space
Odyssey (1968)
Rotation
2001: A Space Odyssey (1968)
Next Lecture
Creating Action
Homework 5th due week from today
(Video analysis of Path of Action)
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