Upcoming Deadlines

1. 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 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 #9 Create 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.

5. 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.

6. 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)

7. 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.

8. WalksPart II

9. Ray Harryhausen Ray 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

10. Energy Budget (Inanimate) Moving objects have an energy budget. For inanimate objects, this budget is: Kinetic Energy (K) – Energy due to their speed Potential Energy (P) – Energy due to their height Friction Loss (F) – Energy lost due to friction forces K = 40 P = 40 F = 20 K = 0 P = 100 F = 0 K = 20 P = 70 F = 10 Total Energy = 100

11. Demo: Ball Races Marbles 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.

12. Demo: Ball Races B) Ball B is the winner. K = 50 P = 50 F = 0 K = 50 P = 50 F = 0 K = 50 P = 50 F = 0 K = 0 P = 100 F = 0 K = 50 P = 50 F = 0 K = 50 P = 50 F = 0 K = 100 P = 0 F = 0 Ball B has a high speed in the center section.

13. Energy Budget, Bouncing Kinetic Energy Potential Energy Friction Losses K = 45 P = 5 F = 0 K = 36 P = 4 F = 10 K = 50 P = 0 F = 0 Total Energy = 50

14. Energy Budget, Sack Drop K = 0 P = 200 F = 0 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? K = ??? P = 100 F = 5 (Air resistance) • Zero • 200 • 100 • 95 • 105 K = 0 P = 0 F = 200 Kinetic Energy Potential Energy Friction Losses

15. Energy Budget, Sack Drop K = 0 P = 200 F = 0 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. K = 95 P = 100 F = 5 (Air resistance) K = 0 P = 0 F = 200 Kinetic Energy Potential Energy Friction Losses

16. Energy Budget (Animate) Animate objects can increase their energy budget by doing work. Work Input (W) – Energy added by doing work. Kinetic Energy Potential Energy Friction Losses Work Input K = 0 P = 0 F = 0 W = +0 K = 300 P = 0 F = 20 W = +320 K = 100 P = 0 F = 10 W = +110

17. Energy Budget in Jumping Slow down as you rise to apex so kinetic energy (K) goes down. K = 90 P = 200 F = 60W = +350 K = 145 P = 150 F = 55W = +350 K = 200 P = 100 F = 50W = +350 Leg muscles do work as you push off when jumping. K = 0 P = 50 F = 0W = 0 Most of the friction loss is during push but a little loss due to air resistance.

18. Energy Budget in Walking K = 100 P = 100 F = 0W = +0 K = 100 P = 100 F = 500W = +500 Walking takes work due to all the frictional losses.

19. 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

20. 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

21. Home Demo: Silly Walks Try walking around as John Cleese, the Minister of Silly Walks. You will find that you use much more energy than normal walking.

22. Simplified Walking Model Pelvis 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 Passing Position Stride CG Passing Position Stride Walking Forward Passing Position We have to do work to raise the CG and much of that energy (30-40%) is lost to friction.

23. Pelvic Rotation Without Rotation As the passing leg swings forward, the hips swing around, rotating about the planted leg. With Rotation

24. Pelvic Rotation & Center of Gravity By 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. CG Path of Action ofCG with Rotation Without Rotation Passing Position Stride CG Stride Passing Position Walking Forward Passing Position Walking is more efficient with pelvic rotation.

25. Pelvic List In 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.

26. Pelvic List & Center of Gravity CG Path of Action ofCG without List 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. With Pelvic List Passing Position Stride CG Passing Position Stride Walking Forward Passing Position Walking is more efficient with pelvic list.

27. 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. Walking Forward

28. Knee Flexion Path of Action of CG without Flexion CG Knee 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. With Flexion Passing Position Stride CG Passing Position Stride Walking Forward Passing Position Walking is more efficient with knee flexion.

29. 8-Loop & U-Loop Side-to-Side 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. Up & Down Figure 8Loop Walking Forward Fast Slow

30. Stride Width Shifting the center of gravity from left to right requires work so a wide stride is less efficient.

31. 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

32. Energy & 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. Raise XCG XCG Move

33. Optimum Step Length Longer Steps, Slower Cadence Shorter Steps, Quicker Cadence Treadmill data of metabolic rate while walking at 2½ mph Optimum Step Length Work done per minute Step Length (meters) The body adjusts the step length to minimize the total energy expended while maintaining desired speed.

34. Shoulder Rotation The shoulders rotate opposite from the hips, swinging over the planted leg.

35. Fashion Runway Walk The walk of a fashion model on a runway exaggerates the pelvic and shoulder rotation as well as the pelvic list.

36. 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.

37. Angular Momentum Balance Moving your legs (and hips) as you walk requires a torque (rotational force) to turn them. It takes less effort if you balance the rotation of the lower body with an opposite rotation of your upper body.

38. Home Demo: The Twist Try 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

39. Skeleton Battle Scene Now that we’ve broken down the mechanical elements of walking, lets it watch again.

40. 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.

41. Walking mimics elephants AT-AT Walkers Industrial Light & Magic (ILM) filmed the AT-ATs using stop-motion animation with models from 2 inches to 2 feet in height. Star Wars Episode V: The Empire Strikes Back

42. Shoulder, Elbow, Wrist Front legs of mammals have the same joints but bones are of various lengths. Human Dog ??? Horse Cat Shoulder Elbow Wrist From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones

43. Tennis Shoes & Stripped Socks Chuck Jones presents a good way to remember animal anatomy: Tennis shoes & Stripped socks. Knee Ankle Sole From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones

44. Sole, Ankle, Knee What you think is the “knee” on the hind leg is actually the ankle. Horse Dog Human Knee Ankle Knee Knee Ankle Sole Sole Ankle Sole From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones

45. Energy in Four-legged Walks Four-legged walking gait alternates passing position and stride between fore and hind legs to minimize energy required to lift the center of gravity. x x x x x Center of Gravity Height The Journal of Experimental Biology 207, 3545-3558 (2004)

46. Next LectureEffects Animation Homework 9 (Stop-motion Animation) Due Wednesday, October 28th Please return the clickers!