Upcoming Deadlines Sixth Homework (Stop-motion Animation) Due Tuesday, February 28 th (Next week) 20...
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Upcoming DeadlinesSixth Homework (Stop-motion Animation)Due Tuesday, February 28th (Next week)20 points (if late, 10 points)Bonus prize of 20 extra points to top three.
Seventh Homework (Outline of First Term Paper)Due Tuesday, March 6th (In two weeks)10 points (if late, 5 points)
For full schedule, visit course website:ArtPhysics123.pbworks.comPick up a clicker, find the right channel, and enter Student ID
Homework Assignment #6In this assignment you will create a stop-motion animation of a falling object. It can be a simple as a ball bounce cycle or (preferably) something more interesting, like a flour sack or a water balloon. Because you will have to pose your object at different heights, you'll either need to suspend it from a string or have the motion occur on the ground with the camera positioned directly overhead.
Homework Assignment #6If you have a webcam, an easy way to film a stop-motion animation is to use SAM Animation (http://www.samanimation.com/). It's free software that runs on both Macs and PCs; it was developed at Tufts University as part of a National Science Foundation project for teaching using animation. The software is designed so that it can be used by even elementary school children so you shouldn't have much trouble figuring it out.
Homework Assignment #6
Homework Assignment #6While I encourage you to help each other out, for this assignment each person needs to create their own animation. Finally, describe in a brief paragraph how you created your animation. Post your animation clip to your blog in an entry entitled "Stop Motion Animation of Falling.Due by 8am on Tuesday, February 28th 20 points (if late, 10 points)The top three animation clips in the class will receive a bonus of 20 extra points.
Extra Credit OpportunityAcademy Award Nominated Animated Short Films
Camera 3 theater in downtown San Jose
Turn in your ticket stub for 5 points extra credit.
Extra Credit OpportunityArt of Dreamworks Puss in Boots at the Cartoon Art Museum in San Francisco.For info: cartoonart.orgTurn in proof of your attendance to this exhibition (e.g., ticket receipt) for 10 points extra credit.
Extra Credit OpportunitySee Chico and Rita, now playing at Camera 12 in downtown San Jose.Turn in your ticket stub for 5 points extra credit.
Survey QuestionYou have some experience with creating stop-motion animation.
True or False?
The League of Extraordinary Gentlemen (2003)In this scene, Sean Connery jumps out the side of a speeding car and lands on his feet.http://www.youtube.com/watch?v=n8SDdkKSqns
Roll forward from where he lands, in the direction of the moving car.Roll backwards from where he lands.Land just as he does in the movie; this was actually done by a stuntman.Review QuestionIn this scene, Sean Connery jumps out the side of a speeding car and lands on his feet. In reality, he would:
A) Roll forwardYou are moving at the same speed as the car when you jump out so you will roll forward.
Jumping out of a CarYour pathYoull start losing speed after you hit the ground so, relative to the car, youll fall behind as the car continues speeding along.car
Review QuestionThe accident-prone Wile E Coyote walks off a cliff carrying an anvil.
If he lets go of the anvil, hell fall:
SlowerFasterAt the same speed
Wile E Coyote with AnvilThe answer is:SlowerYou reach terminal speed when the force of air resistance balances your weight.The less you weight, the less air resistance is needed so the terminal speed is also lower (lower speed lower air resistance).
Creating ActionPart II
Newtons Laws of ForcesNewton established three basic laws to explain how motion is caused by forces:
Law of Inertia Law of Acceleration Action-Reaction Principle
The Law of Inertia explains motion without forces (or with only balanced forces). The Law of Acceleration explains motion with unbalanced forces.Sir Isaac Newton
Demo: SpoolPull on string wrapped around a spool. Force is to the right-to-left. In what direction does the spool move?PullPull
Force and DirectionObjects always change their velocity in the direction of the applied force.PullPullMotionMotionMotion
Demo: TricyclePull on tricycle pedal with a string.Which direction does the tricycle move?PullPullPedal in top positionPedal in bottom position
Demo: TricycleNotice that the position of the lower pedal moves forward as the wheel is turning.CLICK
Forces & Slowing In/OutWhen a force pulls in the direction that an object is already moving, the object slows out (accelerates)If a force pushes opposite to the direction of motion then the object slows in (decelerates)ForceMoving this wayForceMoving this way
Forces & Path of ActionWhen a force is perpendicular to the path of action then it deflects the motion into an arc.Force(up & left)Moving this wayIf force is at an arbitrary angle then both timing and path of action are affected.
More Force, More AccelerationThe greater the net force on an object, the greater the acceleration of that object.
Simple Addition of ForcesWhen two forces pull in parallel directions its simple to add them to get the total force.Gravity (Weight)Air ResistanceTotal ForceFor example, if a bubble weighs 3 oz and air resistance is a force of 2 oz then the total force is 1 ounce.
Air Resistance on a Falling ObjectGravity force on an object (i.e., weight) is constant but air resistance depends on an objects speed.
As a falling object gains speed, the resistance force gets larger so the net force decreases. Net force is sum of:Weight (downward)Resistance (upward)Net Force 100 lbs.Net Force 20 lbs.Net Force Zero
More Mass, Less AccelerationThe greater the mass of an object, the less it accelerates when acted on by a force.
Motion Graphs - SpeedFastSlowFrameDistanceGreater the speed, steeper the slope.
Motion Graphs - AccelerationBig AccelerationSmall AccelerationFrameDistanceGreater the acceleration, greater the curvature.
Speed & AccelerationThe change in the spacings gives the acceleration.The spacing between positions gives the speed.
Odd Rule & ForcesThe Odd Rule applies if forces are constant.Forces here are constant; the support force by the ground balances the weight, leaving only the friction force.SupportFrictionGravity (Weight)Apex135
Law of Acceleration (F=ma)If the total force equals the objects weight then the spacing is the same as when falling.If the total force is greater than the weight then the spacings and increments are larger.If the total force is less than the weight then the spacings and increments are shorter.Bigger the frictional force, the quicker the timing (spacings change quickly).Ice blockBrick
Complex Path of Actionhttp://www.youtube.com/watch?v=mbMo4HFJC1YLets look further into why a leaf drop has such a complex path of action.
Timing and Spacing, Up & DownWhen the leaf/paper slides downward, it picks up speed (slows out).* With no windImagine riding a roller coaster.When it rises due to lift* it loses speed (slows in).
Atmospheric PressureThe weight of the air above us creates atmospheric pressure, a force of about 15 pounds per square inch.We live at the bottom of an ocean of fluidthe fluid is air & ocean is the atmosphere.
Demo: Magdeburg HemispheresPair of hemispheres fit together with air-tight sealMost of the air is pumped out from the interior.Air pressure holds the two pieces tightly together.
Demo: Peeps in a VacuumBefore vacuum pump is turned on (normal atmospheric pressure)After vacuum pump is turned on (very low air pressure in chamber)After vacuum pump is removed (back to normal atmospheric pressure)
Total Recall (1990)http://www.youtube.com/watch?v=ILqe_mmtBrE
BuoyancyABuoyant force pushing submerged objects upward is also due to a pressure difference.HHIGH PRESSUREATMOSPHERIC PRESSUREHHIGHER PRESSUREHThe pressure increases with depth due to the weight of the liquid.
Demo: Neutral Buoyancy BalloonTie a helium balloon to a long string and allow it to float upward until it can lift no more string.Cut the string where it touches the floor.Weight of balloon and string exactly balance the buoyant force.
Demo: Boyles LawThe pressure in a gas increases when the gas is compressed.
When a gas expands, the pressure decreases.Compress the gas by pushing in the syringe. Dial gauge shows increase in pressure.SyringeGaugeTank
Breathing & Boyles LawLAAH
Demo: Drinking StrawLAAWith lungs, you reduce pressure in your mouth and in the straw.
The higher pressure on the outside pushes the liquid up the straw.
Force due to the pressure difference must match or exceed the weight.WeightNO SUCKING FORCE
Prairie Dog VacuumPrairie dogs captured by giant vacuum truck with a padded bin.
The Curse of the Were-Rabbit (2005)
Vacuum Cleaner ForceLAForceAs with any vacuum cleaner, its the difference of pressure that creates the net force pushing objects towards the low pressure side. TruckA
Fluid Flow and PressurePressure varies when air is moving and we see this effect in the flapping of a flag and the ocean waves kicked up by a strong wind.These pressure variations are primarily not due to changes of density or temperature. In fact, most fluid simulations assume air to be incompressible and at constant temperature.
Pressure & Air