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Upcoming Classes

Upcoming Classes. Tuesday, Sept. 25 th Entropy and the Second Law Assignment due: * Read “Exploiting Heat”, The New Way Things Work, D. Macaulay, Pages 142-157 Thursday, Sept. 27 th First set of Oral Presentations Assignment due: * First term paper or oral presentation.

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Upcoming Classes

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  1. Upcoming Classes Tuesday, Sept. 25th Entropy and the Second Law Assignment due: * Read “Exploiting Heat”, The New Way Things Work, D. Macaulay, Pages 142-157 Thursday, Sept. 27th First set of Oral Presentations Assignment due: * First term paper or oral presentation

  2. Upcoming Classes Thursday, Sept. 27th First set of Oral Presentations Assignment due: * First term paper or oral presentation Tuesday, Oct. 2nd Midterm Exam Assignment due: * Study for the midterm

  3. Upcoming Deadlines Thursday, September 27th First Set of Oral Presentations First term paper (if not giving presentation) Thursday, October 11th Outline of second oral presentation or written paper

  4. Oral Presentations The following persons will give oral presentations on Thursday, September 27th : • Batres, Adan • Boyd, Heidi • Chen, Emily • Kwiatkowski, Dajon • Lebedeff, Christopher • Lipton, Christopher For everyone else, your first term paper is due on that date.

  5. Oral Presentations (II) The following persons will give oral presentations on Tuesday, November 6th : • Luttrell,Katherine • Macdonald,Keith • McDonald,Kathleen • Mendoza,Jazmin • Nguyen,Jennifer • Nguyen,Linda For everyone else, term paper is due on that date.

  6. Midterm Exam Midterm exam will consist of four short essay questions. Material up to and including: “Energy and the First Law” lecture; “The Mechanics of Movement” reading. Closed book but allowed one page of notes (front & back). Sample questions: “List three ways that a painter can create a sense of distance in a painting. Describe one of the ways in detail.” “What is a fractal? Give two examples of fractals and an example of something that is not a fractal.” “Explain the physics of balance. Give examples related to dance.” Midterm counts for one homework assignment.

  7. Extra Credit: SF Museum of Art Visit San Francisco Museum of Modern Art and see Abstract Expressionist paintings. Turn in your ticket receipt ($7 for students). Worth one homework assignment; deadline is Oct. 16th Guardians of the Secret, Jackson Pollock, 1943

  8. Extra Credit: San Jose Ballet See a performance of San Jose Ballet in San Jose Center for Performing Arts (Nov. 15th – 18th ). Turn in your ticket receipt. Worth one homework assignment or three quiz/participation credits. Ramon Moreno in CARMINA BURANA

  9. Extra Credit: Cypress Quartet SJSU Celebrates 150th with Cypress String Quartet Event Fusing Precision Playing with World-Class Technology SJSU Music Concert Hall, 7 p.m. Thur., Sept. 20th. TONIGHT! I will hand out tickets at the door from 6:30 to 6:50pm; don’t be late to the performance! Worth two quiz/participation extra credits.

  10. David Chai, Animator Your flip-book homework was judged by David Chai of Thunderbean Animation Studios and San Jose State University.

  11. Energy & The First Law

  12. Design Design is often a blending of art & science Architecture Fashion Design Product Design & Graphic Design

  13. Physics of Drapery Drapery is a surprisingly difficult physics problem Elements of Draping Proceedings of the National Academy of Sciences (2004) Artist’s drawing (A. Durer, 1500) Vera Wang Wedding Dress (2006)

  14. Frank Gehry, Architect Modern engineering and science tell us that the designs of Frank Gehry can be built and are safe. Fundamental question in design: What are the limitations placed by the laws of physics? Disney Concert Hall, Los Angeles MIT, Boston Hotel in Spain

  15. Fundamental Design Questions Can you design a machine that creates a large force using a small force? Can you design a machine that creates a lot of energy using a little energy? Burj Dubai Hybrid car

  16. Kinetic Energy (KE) Kinetic energy is energy of motion. Kinetic energy of an object is, (Kinetic Energy) = ½ x (Mass) x (Speed)2 A stationary object has zero kinetic energy. Supertanker and bullet both have large kinetic energies

  17. Potential Energy (PE) Gravitational potential energy of an object is, (Potential Energy) = (Weight) x (Height) Think of potential energy as stored energy or energy “in the bank.” Metric unit of energy is Joules.

  18. 10 m PE = 600 J, KE = 600 J The First Law PE = 1200 J, KE = 0 J 6 kg Energy is the “currency” of motion Ramp 20 m Roller Coaster PE = 0 J, KE = 1200 J Can calculate the kinetic and potential energy of a falling bowling ball

  19. Conservation of Energy Conservation of mechanical energy is (Potential Energy) + (Kinetic Energy) stays constant during motion. Energy “bookkeeping” makes motion simple.

  20. Types of Energy In this lecture we’ll consider mechanical energy but there’s also: • Thermal energy • Chemical energy • Electrical energy • Solar energy* • Nuclear energy Total energy is conserved, once we account for the various different forms it can transform into. * Actually a form of electrical energy

  21. Demo: Ball Races Which ball wins the race, A or B? Ball on track B has less potential, thus more kinetic energy (and greater speed) during most of the race.

  22. Energy and Force To stop an object with a large kinetic energy requires either: • Large force (stopping the object quickly). • Small force applied for a long distance. Notice that changing object’s energy depends on force and distance.

  23. Demo: Egg Throw Throw a raw egg as fast as possible at a plastic sheet that’s held loosely. X X X X X (Hold here)

  24. (FORCE) x (distance) Ouch! X X Demo: Vampire Stake Place a heavy stake on my chest and strike with a hammer. Why am I not killed? (force) x (DISTANCE) Not safe if stake strikes hard skull Soft, fleshy chest

  25. Crumple Zones Air Bags Seatbelts Automobile Safety Maximizing the distance during impact on the driver minimizes the force of impact. Used in design of:

  26. Work Define work done on an object by a force as (Work) = (Force) X (Distance traveled) Force acting in direction of motion: Positive work. Force acting in opposite direction: Negative work. Force perpendicular to motion: Zero work Change in energy equals the work done on by forces

  27. Check Yourself Slaves pull a heavy load. Work done by slaves is positive, negative, or zero? Positive work. Work done by friction force? Negative work. Work done by the ground? Zero. Support does no work. Support Pull Friction LOAD

  28. Ramp (Inclined Plane) Ramps allow us to lift a heavy object using a small force by pushing over long distance. (small force) X (LONG DISTANCE) (BIG FORCE) X (short distance) Two persons do the same work but exert different forces.

  29. Pyramids Ramps allowed ancient civilizations to lift enormous stones to build pyramids

  30. Knife Knife is a wedge that exerts a large force over a small distance by exerting a small force over a large distance. Wedge exerts large force for a small distance Push down large distance with small force

  31. Zipper The zipper, patented in 1917, has interlocking teeth separated or joined by a wedge. Wedge Gideon Sundback’s patent for the "Separable Fastener"

  32. Lever Lever also converts a small force into a large force by ratio of distances acting. Push down with a small force over a large distance Lift a large weight over a small distance

  33. First Class Levers Fulcrum is located in between the input force (effort) and the output force (load) Load Arm Effort Arm Fulcrum (Load force)/(Effort force) = (Effort Arm)/(Load Arm)

  34. Second & Third Class Levers Load Arm Effort Arm Second Class Lever (Effort, Load, Fulcrum) Load Arm Effort Arm Third Class Lever (Load, Effort, Fulcrum)

  35. Load Effort Fulcrum Examples of Levers Scissors Crowbar Trebuchet Wheel barrow

  36. Human Arm as a Lever Bicep muscle exerts an effort force close to your elbow (fulcrum) to raise your forearm (load). This is a third class lever so a large effort force acts over a small distance to move a small load over a large distance.

  37. Cantilever Cantilevers are used in architecture to support hanging beams and platforms Support Weight Cantilever Effort Load Fulcrum Fallingwater house (1935) designed by Frank Lloyd Wright

  38. Piano Key A piano key a simple lever that when pressed down by a pianist, pushes up against another lever, the whippen. Effort Whippen Load Fulcrum

  39. Whippen Lever As the capstan pushes up the whippen, which then pushes the jack upwards against the hammer while pushing the spoon towards the damper. Load jack whippen Effort capstan

  40. Jack & Hammer Load Load Hammer Effort Effort Jack Jack Jack rises, pushes the hammer towards the string, then is pulled away from the hammer when it hits the letoff button. Hammer swings and hits the string.

  41. Demo: Hanging Hammer Oddly, the hinge doesn’t open when the hammer hangs from the board. Why? Hinge If the hinge opened then the center of gravity, located near the hammer’s head, would rise. This would be a spontaneous increase in the potential energy of an object at rest. That’s impossible, in the same way that a ball won’t spontaneously roll uphill. Center of Gravity

  42. Perpetual Motion Machines Is it possible to design a machine that runs forever, creating its own source of energy? No. By the First Law, energy may be transferred from one form to another but it may neither be created nor destroyed. Perpetual motion machines are impossible, but that’s not stopped people from trying.

  43. Overbalanced Wheel Leonardo da Vinci’s notebooks show his analysis of perpetual motion ideas that originated in 8th century India and reached Europe via Arabia Wheel seems to perpetually turn due to imbalance between left and right sides

  44. Perpetual Motion & Levers Overbalanced wheel may appear as if could start from rest, begin turning and continue to turn clockwise forever. Does not turn at all because the weights on the left have a shorter effort arm than the load arm on the right. Load Arm Effort Arm Load Effort You might set yourself to prove that by equipping such a wheel with many balances, … the wheel would stand in perpetual movement. But by this you would be deceiving yourself. Leonardo da Vinci

  45. Perpetual Motion & Ramps Will the chain of balls rotate clockwise or counter-clockwise? Neither since the energy gained going up one side of the ramp exactly equals the energy lost going down the other side.

  46. U.S. Patent Office From General Information Concerning Patents: “A working model, or other physical exhibit, may be required by the Office if deemed necessary. This is not done very often. A working model may be requested in the case of applications for patent for alleged perpetual motion devices.” "It may be perpetual motion, but it will take forever to test it." Cartoon by Donald Simanek.

  47. Next LectureEntropy & the Second Law Remember: Assignment due: Read “Exploiting Heat”, The New Way Things Work, D. Macaulay, Pages 142-157

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