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Upcoming Deadlines. Ninth Homework (Stop-Motion Animation) Due Wednesday, October 28 th (This week) Tenth Homework (Outline of Second Paper) Due Wednesday, November 4 th (Next week) Second Term Paper Wednesday, November 25 th (Day before Thanksgiving; no class that day) - PowerPoint PPT Presentation

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  • Upcoming DeadlinesNinth 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 OpportunitySurvey 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?

    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 OpportunitySurvey 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?

    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 characters 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 #10Outline 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 #10Your 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 1940s to the 1970s 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 forcesK = 0P = 100F = 0K = 20P = 70F = 10K = 40P = 40F = 20Total 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 RacesB) Ball B is the winner.K = 0P = 100F = 0K = 50P = 50F = 0K = 50P = 50F = 0K = 50P = 50F = 0K = 50P = 50F = 0K = 100P = 0F = 0K = 50P = 50F = 0Ball B has a high speed in the center section.

  • Energy Budget, BouncingK = 45P = 5F = 0K = 50P = 0F = 0K = 36P = 4F = 10Kinetic EnergyPotential EnergyFriction LossesTotal Energy = 50

  • Energy Budget, Sack DropK = 0P = 200F = 0K = 0P = 0F = 200K = ???P = 100F = 5Kinetic EnergyPotential EnergyFriction LossesFlour 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?Zero20010095105(Air resistance)

  • Energy Budget, Sack DropK = 0P = 200F = 0K = 0P = 0F = 200K = 95P = 100F = 5Kinetic EnergyPotential EnergyFriction LossesD) 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 = +0Kinetic EnergyPotential EnergyFriction LossesWork InputK = 100P = 0F = 10W = +110K = 300P = 0F = 20W = +320

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

  • Muscle Activity, Moving LegMuscles 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, OConnor

  • Muscle Activity, Planted LegFor the planted leg there is relatively little muscle activity in the middle of the passing position.From Dynamics of Human Gait, by Vaughan, Davis, OConnor

  • 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.CGCGPassing PositionPassing PositionStrideStridePassing PositionWe 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.WithoutRotationWithRotation

  • 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.CGStridePassing PositionPassing PositionPassing PositionStrideCGWalking is more efficient with pelvic rotation.Path of Action of CG with RotationWithout Rotation

  • 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 GravityPelvic 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. CGStridePassing PositionPassing PositionPassing PositionStrideCGWalking is more efficient with pelvic list.Path of Action of CG without ListWith Pelvic List

  • Knee Flexion of Weighted LegKnee flexes about 15 degrees immediately after heel strike and remains flexed until the center of gravity passes over the weight bearing leg.

  • 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.CGStridePassing PositionPassing PositionPassing PositionStrideCGPath of Action of CG without FlexionWith FlexionWalking is more efficient with knee flexion.

  • 8-Loop & U-LoopThe 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.SlowFastSide-to-SideUp & DownWalking ForwardFigure 8 Loop

  • Stride WidthShifting the center of gravity from left to right requires work so a wide stride is less efficient.

  • Step LengthWhen walking, why dont 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.MoveRaiseXCGXCGEnergy & Step Length

  • Optimum Step LengthWork done per minuteStep Length (meters)Treadmill data of metabolic rate while walking at 2 mphOptimum Step LengthLonger Steps, Slower CadenceShorter Steps, Quicker CadenceThe 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 WalkThe walk of a fashion model on a runway exaggerates the pelvic and shoulder rotation as well as the pelvic list.

  • Arm SwingThe 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 BalanceIt takes less effort if you balance the rotation of the lower body with an opposite rotation of your upper bo