Upcoming Deadlines
description
Transcript of Upcoming Deadlines
Upcoming Deadlines
Ninth Homework (Stop-Motion Animation)Due Wednesday, October 28th (This week)
Tenth Homework (Outline of Second Paper)Due Wednesday, November 4th (Next week)
Second Term PaperWednesday, November 25th (Day before Thanksgiving; no class that day)
For full schedule, visit course website:ArtPhysics123.pbworks.com
Extra Credit Opportunity
Survey Questions:1. What do you like most about the course?2. What do you dislike most about the
course?3. What changes would you suggest?4. Do you have any other comments?
Complete anonymous online survey by October 30th; five points extra credit.
Go to course website for link to survey.After completing survey, follow the instructions to receive extra credit.
Extra Credit Opportunity
Survey Questions:1. What do you like most about the course?2. What do you dislike most about the
course?3. What changes would you suggest?4. Do you have any other comments?
Complete anonymous online survey by October 30th; five points extra credit.
Go to course website for link to survey.After completing survey, follow the instructions to receive extra credit.
Opportunity Ends This Friday!
Homework Assignment #9Create a simple stop-motion animation of a moving
character. See course website for software options for creating this
animation.Make the character’s motion look as real and seem as believable
as you possibly can.Due by 8am on Wednesday, October 28th.20 points (if late, 10 points)The top three clips in the class will receive a bonus of 20 extra
points.
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.
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)
Activating your Clicker
* Turn on your clicker.* Enter the number or letter that I give
you for joining this class. Hit Enter/Send key.
* Clicker should read PHY123SCI2* Type in your student ID; hit Enter/Send.Clicker is now ready to use.Hit any key to wake the clicker from sleep mode.
WalksPart II
Ray HarryhausenRay Harryhausen, the master of stop-motion animation, created the special effects in many films from the 1940’s to the 1970’s
One of his best scenes in the skeleton battle in Jason and the Argonauts
Energy Budget (Inanimate)Moving objects have an energy budget.For inanimate objects, this budget is:
Kinetic Energy (K) – Energy due to their speedPotential Energy (P) – Energy due to their heightFriction Loss (F) – Energy lost due to friction forces
K = 0P = 100F = 0
K = 20P = 70F = 10
K = 40P = 40F = 20
Total Energy = 100
Demo: Ball RacesMarbles start at equal height and race on
these rail tracks (almost no friction).Track B has a long dip in the center.
Winner? A) Ball A; B) Ball B; C) Near perfect tie.Hint: Kinetic energy + Potential energy stays constant.
Demo: Ball Races
B) Ball B is the winner.
K = 0P = 100F = 0
K = 50P = 50F = 0
K = 50P = 50F = 0
K = 50P = 50F = 0
K = 50P = 50F = 0
K = 100P = 0F = 0
K = 50P = 50F = 0
Ball B has a high speed in the center section.
Energy Budget, Bouncing
K = 45P = 5F = 0
K = 50P = 0F = 0
K = 36P = 4F = 10
Kinetic EnergyPotential EnergyFriction Losses
Total Energy = 50
Energy Budget, Sack DropK = 0P = 200F = 0
K = 0P = 0F = 200
K = ???P = 100F = 5
Kinetic EnergyPotential EnergyFriction Losses
Flour sack sitting on a shelf starts with potential energy.
After it settles, all the energy is lost to friction forces.
What is the kinetic energy when fallen half-way down?
A) ZeroB) 200C) 100D) 95E) 105
(Air resistance)
Energy Budget, Sack DropK = 0P = 200F = 0
K = 0P = 0F = 200
K = 95P = 100F = 5
Kinetic EnergyPotential EnergyFriction Losses
D) 95
The total budget (K+P+F) has to equal 200.
If there was no air resistance then the falling speed would be greater and K=100.
With more air resistance, the friction loss would be greater and kinetic energy less.
(Air resistance)
Energy Budget (Animate)Animate objects can increase their energy budget by doing work.
Work Input (W) – Energy added by doing work.
K = 0P = 0F = 0W = +0
Kinetic EnergyPotential EnergyFriction LossesWork Input
K = 100P = 0F = 10W = +110
K = 300P = 0F = 20W = +320
Energy Budget in Jumping
K = 0P = 50F = 0W = 0
K = 200P = 100F = 50W = +350
K = 145P = 150F = 55W = +350
K = 90P = 200F = 60W = +350Leg muscles
do work as you push off when jumping.
Slow down as you rise to apex so kinetic energy (K) goes down.
Most of the friction loss is during push but a little loss due to air resistance.
Energy Budget in Walking
K = 100P = 100F = 500W = +500
K = 100P = 100F = 0W = +0
Walking takes work due to all the frictional losses.
Muscle Activity, Moving Leg
Muscles in the moving leg accelerate it forward after toe-off and decelerate at the heel strike. Also hold the foot up.
From Dynamics of Human Gait, by Vaughan, Davis, O’Connor Activity: High ; Medium ; Low
Muscle Activity, Planted Leg
For the planted leg there is relatively little muscle activity in the middle of the passing position.
From Dynamics of Human Gait, by Vaughan, Davis, O’Connor Activity: High ; Medium ; Low
Home Demo: Silly WalksTry walking around as John Cleese, the Minister of Silly Walks.
You will find that you use much more energy than normal walking.
Simplified Walking ModelPelvis is a double-forked bar with spherical hip joints. Legs are straight bars without knees, ankles, or feet.
Center of gravity rises and falls as an inverted pendulum.
CG
CG
Passing Position
Passing Position
Stride
Stride
Passing Position
Walking Forward
We have to do work to raise the CG and much of that energy (30-40%) is lost to friction.
Pelvic RotationAs the passing leg swings forward, the hips swing around, rotating about the planted leg.
WithoutRotation
WithRotation
Pelvic Rotation & Center of GravityBy permitting the pelvis to rotate from left-to-right (and right-to-left) the center of gravity does not fall as far during the stride.
CGStride
Passing Position
Passing Position
Passing Position
Stride
CG
Walking is more efficient with pelvic rotation.
Path of Action ofCG with Rotation
Without Rotation
Walki
ng Forw
ard
Pelvic ListIn the passing position the pelvis drops slightly to the non-weight bearing side. This motion is called “pelvic list.”
Note that the knee has to bend to lift the foot, otherwise it would drag the ground.
Pelvic List & Center of Gravity
Pelvic list keeps the center of gravity from rising as much when the body passes over the weight-bearing leg, keeping the center of gravity on a flatter path of action.
CG
Stride
Passing Position
Passing Position
Passing Position
Stride
CG
Walking is more efficient with pelvic list.
Path of Action ofCG without List
With Pelvic List
Walki
ng Forw
ard
Knee Flexion of Weighted Leg
Knee flexes about 15 degrees immediately after heel strike and remains flexed until the center of gravity passes over the weight bearing leg.
Walki
ng Forw
ard
Knee FlexionKnee flexion keeps the center of gravity from rising as much during the passing position.
Knee flexion also reduces the impact on the body at heel strike.
CG
Stride
Passing Position
Passing Position
Passing Position
Stride
CGPath of Action of CG without Flexion
With Flexion
Walki
ng Forw
ard
Walking is more efficient with knee flexion.
8-Loop & U-Loop
The center of gravity shifts up & down but also side-to-side. CG makes a Figure-8 loop when walking slow
Makes a U-shape loop when walking fast.
Slow Fast
Side-to-Side
Up & Down
Walking
Forward
Figure 8Loop
Stride WidthShifting the center of gravity from left to right requires work so a wide stride is less efficient.
Step Length
When walking, why don’t we take longer (or shorter) steps?We naturally adjust our step length to minimize the energy output required to maintain our desired walking speed.
Step length
Energy is required to:
• Move the leg forward in the stride; longer steps take less energy.
• Raise the body in the passing position; longer steps take more energy.
Move
Raise
XCGXCG
Energy & Step Length
Optimum Step Length
Work
don
e p
er
min
ute
Step Length (meters)
Treadmill data of metabolic rate while walking at 2½ mph
Optimum Step
Length
Longer Steps, Slower
Cadence
Shorter Steps,
Quicker Cadence
The body adjusts the step length to minimize the total energy expended while maintaining desired speed.
Shoulder RotationThe shoulders rotate opposite from the hips, swinging over the planted leg.
Fashion Runway Walk
The walk of a fashion model on a runway exaggerates the pelvic and shoulder rotation as well as the pelvic list.
Arm Swing
The arm swings back and forth, also like a pendulum, roughly 180o out of phase with the leg. The arm and leg are roughly the same length so they swing back and forth with about the same period.
Angular Momentum Balance
It takes less effort if you balance the rotation of the lower body with an opposite rotation of your upper body.
Moving your legs (and hips) as you walk requires a torque (rotational force) to turn them.
Home Demo: The TwistTry dancing The Twist the normal way (moving hips and shoulders in opposite directions). Now try to dance it moving hips and shoulders together, back and forth.
Play
Skeleton Battle Scene
Now that we’ve broken down the mechanical elements of walking, lets it watch again.
Quadruped Animal Walking
Walking for animals is very different than for humans, not so much because they walk on 4 legs but due to bone structure.
AT-AT WalkersIndustrial Light & Magic (ILM) filmed the AT-ATs using stop-motion animation with models from 2 inches to 2 feet in height.
Walking mimics elephants
Star Wars Episode V: The Empire Strikes Back
Shoulder, Elbow, WristFront legs of mammals have the same joints but bones are of various lengths.
From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones
Shoulder
Elbow
Wrist
Horse Human Dog Cat ???
Tennis Shoes & Stripped Socks
From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones
Chuck Jones presents a good way to remember animal anatomy: Tennis shoes & Stripped socks.
Knee
Ankle
Sole
Sole, Ankle, Knee
From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones
Knee
Ankle
Sole
Knee
Knee
Ankle
Ankle
Sole
Sole
HorseHuman Dog
What you think is the “knee” on the hind leg is actually the ankle.
Energy in Four-legged WalksH
eig
ht
x x x x x
Center of Gravity
Four-legged walking gait alternates passing position and stride between fore and hind legs to minimize energy required to lift the center of gravity.
The Journal of Experimental Biology 207, 3545-3558 (2004)
Next LectureEffects Animation
Homework 9 (Stop-motion Animation)Due Wednesday, October 28th
Please return the clickers!