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									              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
              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
        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
          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.
        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.
                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
Midterm counts for one homework assignment.
     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
      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
            Extra Credit: Cypress Quartet
 SJSU Celebrates 150th with Cypress String
   Quartet Event Fusing Precision Playing with
   World-Class Technology            TONIGHT!
 SJSU Music Concert Hall, 7 p.m. Thur., Sept. 20th.
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.
        David Chai, Animator
Your flip-book homework was judged by David Chai
  of Thunderbean Animation Studios and San Jose
  State University.
  Energy &
The First Law
Design is often a blending of art & science


                               Product Design &
                               Graphic Design
                     Physics of Drapery
Drapery is a surprisingly difficult physics problem

                                                      Elements of Draping
  Artist’s drawing
                            Vera Wang                 Proceedings of the
  (A. Durer, 1500)                                    National Academy
                           Wedding Dress
                              (2006)                  of Sciences (2004)
            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      MIT, Boston
                                     Hall, Los Angeles

     Hotel in Spain
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?


                      Hybrid car
          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
        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.
                       The First Law
                        PE = 1200 J, KE = 0 J
              6 kg

                            Energy is the “currency” of motion
       10 m

                                                  PE = 600 J, KE = 600 J
20 m


                        PE = 0 J, KE = 1200 J

 Can calculate the kinetic and potential energy of a falling bowling ball
      Conservation of Energy
Conservation of mechanical energy is

 (Potential Energy) + (Kinetic Energy)

stays constant during motion.

Energy “bookkeeping” makes motion simple.
            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
            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.
          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.
       Demo: Egg Throw
Throw a raw egg       X           X
 as fast as
 possible at a
 plastic sheet    X

 that’s held              X

                              X (Hold here)
          Demo: Vampire Stake
Place a heavy stake on my chest and strike
  with a hammer. Why am I not killed?
 (force) x (DISTANCE)     (FORCE) x (distance)

                                X X

                                       Not safe if stake
                                       strikes hard skull
            Automobile Safety
Maximizing the distance during impact on the driver
 minimizes the force of impact. Used in design of:

    Seatbelts         Air Bags           Crumple
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
            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?         Friction
Zero. Support does no work.
        Ramp (Inclined Plane)
Ramps allow us to lift a heavy object using a
 small force by pushing over long distance.

  (small force)
                                            (BIG FORCE)
                                              X (short distance)

Two persons do the same work but exert different forces.
Ramps allowed ancient
civilizations to lift
enormous stones to
build pyramids
  Knife is a wedge that exerts a large force
   over a small distance by exerting a small
   force over a large distance.
Push down        Wedge exerts
large distance   large force for a
with small       small distance
The zipper, patented in 1917, has interlocking
 teeth separated or joined by a wedge.


 Gideon Sundback’s patent for the "Separable Fastener"
Lever also converts a small force into a
  large force by ratio of distances acting.

Push down                         Lift a large
with a small                      weight over a
force over a                      small distance
large distance
            First Class Levers
Fulcrum is located in between the input
 force (effort) and the output force (load)

           Arm             Effort Arm


 (Load force)/(Effort force) = (Effort Arm)/(Load Arm)
   Second & Third Class Levers
                          Effort Arm
Second Class Lever
(Effort, Load, Fulcrum)

                                       Effort Arm
Third Class Lever
(Load, Effort, Fulcrum)
         Examples of Levers



                   Wheel barrow
          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
Cantilevers are used in architecture to
 support hanging beams and platforms

  Effort     Cantilever

                                  Fallingwater house (1935)
                                  designed by Frank Lloyd Wright
                 Piano Key
                    A piano key a simple
                      lever that when
                      pressed down by a
                      pianist, pushes up
                      against another
                      lever, the whippen.

          Load        Fulcrum
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.



                     Jack & Hammer


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.
          Demo: Hanging Hammer
Oddly, the hinge doesn’t open when the
 hammer hangs from the board. Why?
If the hinge opened then the       Hinge
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    Center of
same way that a ball won’t          Gravity
spontaneously roll uphill.
    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.
             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
        Perpetual Motion & Levers
        Load           Effort Arm
                                             Overbalanced wheel may
                                               appear as if could start
 Load                                          from rest, begin turning
                                               and continue to turn
                                        Effort clockwise forever.

                                             Does not turn at all
                                               because the weights on
                                               the left have a shorter
You might set yourself to prove that by
equipping such a wheel with many balances, …   effort arm than the load
the wheel would stand in perpetual movement.
But by this you would be deceiving yourself.   arm on the right.
                 Leonardo da Vinci
    Perpetual Motion & Ramps
Will the chain of balls rotate clockwise or
Neither since the
energy gained
going up one side
of the ramp exactly
equals the energy
lost going down the
other side.
           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.
     Next Lecture
Entropy & the Second Law

        Assignment due:
      Read “Exploiting Heat”,
   The New Way Things Work,
   D. Macaulay, Pages 142-157

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