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Upcoming Deadlines

Pick up a clicker, find the right channel, and enter Student ID. Upcoming Deadlines. Sixth Homework (Stop-motion Animation) Due Tuesday, February 28 th (Next week) 20 points (if late, 10 points) Bonus prize of 20 extra points to top three. Seventh Homework (Outline of First Term Paper)

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Upcoming Deadlines

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  1. Pick up a clicker, find the right channel, and enter Student ID Upcoming Deadlines Sixth 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.com

  2. Homework Assignment #6 In 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.

  3. Homework Assignment #6 If 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.

  4. Homework Assignment #6

  5. Homework Assignment #6 While 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.

  6. Extra Credit Opportunity Academy Award Nominated Animated Short Films Camera 3 theater in downtown San Jose Turn in your ticket stub for 5 points extra credit.

  7. Extra Credit Opportunity Art of Dreamworks’ Puss in Boots at the Cartoon Art Museum in San Francisco. Turn in proof of your attendance to this exhibition (e.g., ticket receipt) for 10 points extra credit. For info: cartoonart.org

  8. Extra Credit Opportunity See Chico and Rita,now playing at Camera 12 in downtown San Jose. Turn in your ticket stub for 5 points extra credit.

  9. Survey Question You have some experience with creating stop-motion animation. True or False?

  10. The League of Extraordinary Gentlemen (2003) http://www.youtube.com/watch?v=n8SDdkKSqns In this scene, Sean Connery jumps out the side of a speeding car and lands on his feet.

  11. Review Question In this scene, Sean Connery jumps out the side of a speeding car and lands on his feet. In reality, he would: • 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.

  12. Jumping out of a Car A) Roll forward You are moving at the same speed as the car when you jump out so you will roll forward. Your path car You’ll start losing speed after you hit the ground so, relative to the car, you’ll fall behind as the car continues speeding along.

  13. Review Question • The accident-prone Wile E Coyote walks off a cliff carrying an anvil. • If he lets go of the anvil, he’ll fall: • Slower • Faster • At the same speed

  14. Wile E Coyote with Anvil • The answer is: • Slower You 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).

  15. Creating ActionPart II

  16. Newton’s Laws of Forces • Newton 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

  17. Spool moves? Spool moves? Demo: Spool Pull on string wrapped around a spool. Force is to the right-to-left. In what direction does the spool move? Pull Pull

  18. Force and Direction Objects always change their velocity in the direction of the applied force. Motion Motion Pull Motion Pull

  19. Bike moves? Bike moves? Demo: Tricycle Pull on tricycle pedal with a string. Which direction does the tricycle move? Pedal in bottom position Pedal in top position Pull Pull

  20. Demo: Tricycle Notice that the position of the lower pedal moves forward as the wheel is turning. CLICK

  21. FALLING BALL Forces & Slowing In/Out When a force pulls in the direction that an object is already moving, the object slows out (accelerates) Moving this way Force If a force pushes opposite to the direction of motion then the object slows in (decelerates) RISING BALL Moving this way Force

  22. Forces & Path of Action When a force is perpendicular to the path of action then it deflects the motion into an arc. If force is at an arbitrary angle then both timing and path of action are affected. Force (up & left) Moving this way

  23. More Force, More Acceleration The greater the net force on an object, the greater the acceleration of that object.

  24. Simple Addition of Forces When two forces pull in parallel directions it’s simple to add them to get the total force. Total Force Gravity (Weight) For 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

  25. Air Resistance on a Falling Object Net Force100 lbs. Gravity force on an object (i.e., weight) is constant but air resistance depends on an object’s speed. As a falling object gains speed, the resistance force gets larger so the net force decreases. Net Force20 lbs. Net ForceZero Net force is sum of: Weight (downward) Resistance (upward)

  26. More Mass, Less Acceleration The greater the mass of an object, the less it accelerates when acted on by a force.

  27. Motion Graphs - Speed Greater the speed, steeper the slope. Fast Distance Slow Frame

  28. Motion Graphs - Acceleration Greater the acceleration, greater the curvature. Big Acceleration Distance SmallAcceleration Frame

  29. Speed & Acceleration The spacing between positions gives the speed. The change in the spacings gives the acceleration.

  30. Odd Rule & Forces 1 5 The Odd Rule applies if forces are constant. 3 Support Apex Friction Gravity (Weight) Forces here are constant; the support force by the ground balances the weight, leaving only the friction force.

  31. Law of Acceleration (F=ma) If the total force equals the object’s 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. Ice block Brick Bigger the frictional force, the quicker the timing (spacings change quickly).

  32. Complex Path of Action Let’s look further into why a leaf drop has such a complex path of action. http://www.youtube.com/watch?v=mbMo4HFJC1Y

  33. Timing and Spacing, Up & Down When it rises due to lift* it loses speed (slows in). When the leaf/paper slides downward, it picks up speed (slows out). Imagine riding a roller coaster. * With no wind

  34. Atmospheric Pressure We live at the bottom of an ocean of fluid—the fluid is air & “ocean” is the atmosphere. The weight of the air above us creates atmospheric pressure, a force of about 15 pounds per square inch.

  35. A A L A A - Atmospheric pressure A - Low pressure L Demo: Magdeburg Hemispheres Pair of hemispheres fit together with air-tight seal Most of the air is pumped out from the interior. Air pressure holds the two pieces tightly together.

  36. Demo: Peeps in a Vacuum Before 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)

  37. Total Recall (1990) http://www.youtube.com/watch?v=ILqe_mmtBrE

  38. Buoyancy Buoyant force pushing submerged objects upward is also due to a pressure difference. A ATMOSPHERIC PRESSURE H H HIGH PRESSURE The pressure increases with depth due to the weight of the liquid. H HIGHER PRESSURE

  39. Demo: Neutral Buoyancy Balloon Tie 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.

  40. Demo: Boyle’s Law The pressure in a gas increases when the gas is compressed. When a gas expands, the pressure decreases. Gauge Syringe Tank Compress the gas by pushing in the syringe. Dial gauge shows increase in pressure.

  41. Breathing & Boyle’s Law A A H L

  42. Demo: Drinking Straw With 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. L Weight A A NO “SUCKING” FORCE

  43. Prairie Dog Vacuum Prairie dogs captured by giant vacuum truck with a padded bin.

  44. The Curse of the Were-Rabbit (2005)

  45. Vacuum Cleaner Force As with any vacuum cleaner, it’s the difference of pressure that creates the net force pushing objects towards the low pressure side. A L Force Truck A

  46. Fluid Flow and Pressure Pressure 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.

  47. Pressure & Air Resistance Force of air resistance is due to a difference in pressure. High pressure buildsby compression in front of a falling object while low pressure is created in the wake. LOW PRESSURE L HIGH PRESSURE H

  48. Sailing Ships The wind blowing on a sail also produces a pressure difference, creating the force that moves the ship. H L Wind

  49. Ground-effect Cushion Moving this way L L LOW PRESSURE H H HIGH PRESSURE Flat sheet sliding over a smooth surface compresses the air beneath it and forms a low-friction cushion, allowing it to slide. This ground-effect won’t occur with an irregular leaf or with a rough surface.

  50. Paper Drop Test http://www.youtube.com/watch?v=vKf-vIDSIik

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