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					Domain 5 Teacher Notes
I. Energy
 A. Law of conservation of energy.
    1. Energy can neither be created nor destroyed.
    2. It can be changed into other forms.
 B. Two kinds of energy
 Click here for video clip
    1. Potential energy is stored energy or energy of
       position. Examples: Magnetic, gravitational,
       chemical, elastic, and nuclear
               PE = mgh where m= mass
                                 g = acceleration due to gravity
                                 h = height
    2. Kinetic energy is energy of motion or energy in action.
       Examples: a moving baseball or a roller coaster going
                              KE = ½ mv2
 C.Forms of energy
    1. mechanical energy
       a. Any object which possesses mechanical energy -
          whether it be in the form of potential energy or
          kinetic energy - is able to do work. That is, its
          mechanical energy enables that object to apply a
          force to another object in order to cause it to be
       b. simple machines help us lift, pull, increase
           elevation of heavy things, change the direction of
           the force, increase the force, split things, fasten
           things, and cut things
             i. inclined plane - Ramp, stairs
            ii. wedge – two inclined planes back to back –
                 screwdriver, knife, axe
            iii. screw – inclined plane wrapped around a
                                           Revised Friday, June 1, 2007
          iv. pulley – rope revolves around a fixed point;
               more pulleys make work easier
           v. lever – has a fulcrum – see-saw
           vi. wheel and axle – bicycle, car, doorknob,
               screwdriver in use

            Click here for Simple Machines video clip
    a. mechanical advantage-the number of times a
       machine multiplies an effort force.
    b. Formulas from formula sheet:
                                                          F 
                                                     AMA  R 
             Actual Mechanical Advantage:
                                                          FE 
where FR is Force due to resistance and FE is Force due to effort
                     IMA= Effort Length
                         Resistance Length
    Sample Problem: In a pulley set-up, an effort force of
    50 Newtons lifts a resistance force of 100 Newtons.
    What is the MA of the pulley system?
    Think about which formula to use
            FR             IMA= Effort Length
     AMA 
               
             F      or           Resistance Length
                E   
                                           Revised Sunday, July 8, 2007
       AMA= Fr         M.A. = 100N
            Fe                 50N
                       M.A = 2

  2. Heat, Temperature and Internal Energy
    a. The temperature of an object is directly proportional
       to the average kinetic energy of its particles. As
       temperature goes up, particles move faster.
    b. The Internal Energy of a substance is total of the
       potential and kinetic energy of all its particles.
    c. Energy moving from one location to another is
       known as heat. Objects do not contain heat.
       Instead they contain internal energy.
  3. Chemical energy relates to potential energy stored in
     the bonds between atoms in a compound
            Click for Video Clip

D. Wave energy
   1. Basic Wave Vocabulary:
            a) Amplitude – the height of a wave as
               measured from its equilibrium position.
            b) Frequency – the number of wave cycles per
               unit time
            c) Hertz – common unit for frequency, means
               the same as cycles per second
            d) Wavelength – the distance between two
               identical points on adjacent waves. It is
               often measured “crest to crest.”
            e) Period – the time required to complete one

                                        Revised Sunday, July 8, 2007
2. Types of waves. A wave is a disturbance of a
   medium which transports energy through the
   medium without permanently transporting matter. In
   a wave, particles of the medium are temporarily
   displaced and then return to their original position.
   A. Waves in which the particles of the medium
      move in a direction that is perpendicular to the
      direction of the wave are known as transverse
      waves. Transverse waves require a relatively
      rigid medium in order to transmit their
      energy. Examples of transverse waves include
  Waves on a string

   B. A longitudinal wave is a wave in which particles
      of the medium move in a direction parallel to the
      direction which the wave moves. Examples of
                                     Revised Sunday, July 8, 2007
      longitudinal waves include sound waves.

  C. A surface wave is a wave in which particles of the
     medium undergo a circular motion. Surface waves
     are both longitudinal and transverse. Seismic
     (earthquake) and water waves are examples of
     surface waves.

        Click here for Nature of Waves clip
4. Light
    a. Electromagnetic Spectrum

                                    Revised Sunday, July 8, 2007
  i. colors of visible light - ROYGBIV
  red, orange, yellow, green, blue, indigo, violet
  ii. all electromagnetic waves travel at the speed of
      light 3.0 x 108 m/s in a vacuum.

  Click here for Electromagnetic Spectrum clip (4 min)
 b. Reflection occurs when a wave encounters a new
    medium and bounces off of it.
    i. The Law of Reflection states that the angle of
       incidence (the angle between the incoming
       wave and the normal) must equal the angle of
       reflection (the angle between the reflected
       wave and the normal). The normal is a line
       perpendicular to the surface.

c. Refraction occurs when a wave travels at an angle
   from one medium to another in which its speed is
   different. The difference in speed causes the wave
   to bend. Refraction is why objects in a pool are
   difficult to locate when viewed from above and why
   a pencil looks broken when part of it is placed in a
   glass of water.

                                    Revised Sunday, July 8, 2007
d. Diffraction involves the bending of waves around
   obstacles. Diffraction can occur with any kind of
   wave. Diffraction explains why sound can be
   heard around corners.

                                  Revised Sunday, July 8, 2007
         Diffraction of waves through a slit

 e. Interference
     i. Constructive interference occurs when two
        waves disturb the medium in the same
        way. The disturbance is larger than the
        disturbance of either wave separately.
   ii. Destructive interference is canceling interference
        that occurs when two waves disturb the
        medium in opposite ways. The disturbance is
        smaller than the disturbance of either wave

Click here for Wave Interference clip
     Stop clip after Doppler Effect

                                        Revised Sunday, July 8, 2007
    5. Sound
       a. Sound waves are mechanical waves, meaning
          they must have a medium to travel through.
          (There is no sound in space.) A sound wave is a
          compressional or longitudinal wave. This means
          the particles of the medium move in the same
          direction as the wave.
             Click here for a Sound Energy video clip
       b. Sound travels fastest in solids, second fastest in
          liquids, and slowest in gases. As the temperature
          increases, the speed of sound also increases.
          Different sounds appear different because they
          have different pitch or frequency.
             Click here for video clip

II. Forces
   A. gravitational
     1. The force of gravity between any two objects
        increases as the mass of either object increases. The
        force of gravity decreases as the distance between
        the objects increases.

    2. The force of gravity experienced by something is also
       known as its weight. Weight can be calculated
       multiplying mass by the acceleration of gravity (g).
       Weight depends on both mass and the acceleration
       of gravity. Mass depends only on the amount of
       matter in an object. Mass does not change when the
       location of an object changes.
                      Click here for video clip
                                         Revised Sunday, July 8, 2007
     The force and weight are both measured in Newtons.
     Mass is measured in kilograms. Acceleration is
     measured in m/s/s (m/s2).

    3. Free Fall
       a. A free-falling object is an object which is falling
          under the sole influence of gravity.
       b. Free-falling objects do not encounter air
       c. All free-falling objects (on Earth) accelerate
          downwards at a rate of approximately 10 m/s/s
          (to be more exact, 9.8 m/s/s). This quantity
          known as the acceleration of gravity has a
          special symbol to denote it - the symbol g.
          The distance traveled by a falling object is
          calculated using the formula, d = ½ gt2

       d. Sample problem: A rock is dropped from the
          top of a cliff and strikes the ground 6.5
          seconds later. How high is the cliff in meters?
    g=9.8 m/sec2          d = ½ gt2
    t = 6.5 sec             = ½ (9.8 m/sec2) (6.5 sec)2
                            = ½ (9.8 m/sec2) (42.25 sec2)
                            = ½ (414.05 m)
                            = 207 m

B. Electromagnetic Forces – Like charges repel each
   other, opposite charges attract.
   1. As the distance between the charges increase, the
      magnitude of the force decreases. The same holds
      true for magnets.
   2. Magnets will always have a North Pole and a South
                                         Revised Sunday, July 8, 2007
     Pole. Just like with electrical charges, opposite
     poles attract. While it is possible to separate
     positive and negative charges, it is impossible
     to separate north and south magnetic poles.

  3. Electric and Magnetic Field Lines- The lines always
     go from positive charges to negative charges and
     from north poles to south poles. The closer the
     lines, the stronger the field.
                                         Magnetic field is strongest where the lines
                                         are closer together

C.Electromagnet                1. List a use for electromagnets.

                                  Lift and move cars in a junk yard

                               2. How can you make a stronger
                                  a. More coils of wire around the nail
                                  b. More batteries

           Click here for video clip

D. Work
  1. two conditions must be met for work to occur
      a. the object must move through a distance
                                           Revised Sunday, July 8, 2007
        b. a force must act upon the object in the direction
           the object moves
        Click here for video clip
    2. SI unit for work is the joule, J. (Newton-meter)
    3. Formula: work = force X distance W=F X d
    4. When an object is lifted to a new location or pushed
        up a ramp, the work equals the potential energy
    5. Sample Problem: What work is done if Hernando
       uses 88 N of force to pull a table 12 meters?
        F = 88N       Use the formula    W=F X d
        d = 12 m       from the          W=88N X 12 m
    SCIENCE FACTS AND FORMULAS sheet     W= 1056 N-m or
                                            1056 J
 E. Power
  1. the rate of work
  2. SI unit is the watt, W (joule/second)
  3. formula: power = work/time (work divided by time)
  4. Sample Problem: When doing a chin-up, a physics
student lifts her 40-kg body [which has a force (weight) of
400 N] a distance of 0.25 meters in 2 seconds. What is the
power delivered by the student's biceps?
You must first calculate the work done to lift her body
                             = (400 N) (0.25 m)
                           W = 100 J
To calculate power
                 Power= work
               Power=100 J
                     2 sec
                                         Revised Sunday, July 8, 2007
             Power = 50 Watts
III. Motion
   A. Newton’s Laws of Motion
     1. The Law of Inertia or Newton’s First Law: An
        object at rest tends to stay at rest and an object
        in motion tends to remain in motion in a
        straight-line path unless acted on by an
        unbalanced force.
        a. Inertia is another word for mass. The more
            mass an object has, the greater its tendency
           to maintain its current state.
  Click here for video clip
       b. Applications:
           i. People are often thrown from automobiles
              in wrecks because the car comes to a
              sudden stop, but the person has a
              tendency to stay in motion.
          ii. The ride is much smoother on a cruise ship
              than a fishing boat, because the cruise ship
              is more massive and is not affected as
              much by the waves.
   2. Newton’s Second Law: The acceleration of an
      object is directly proportional to the applied force
      and inversely proportional to its mass.
                   F=ma            F= force
                                   m = mass
                                   a = acceleration
              Click here for video clip

                                          Revised Sunday, July 8, 2007
       Sample Problem: What is the force exerted by a
       2 kg mass that accelerates at 3 m/sec/sec?
mass=2 kg                F=ma
acceleration=3 m/sec/sec F =2 kg x 3 m/sec/sec
                             F=6 kilogrammeter/sec/sec

        Check the SCIENCE FACTS AND FORMULAS sheet
               1 newton = 1 kilogrammeter/second/second

         So the correct answer is 6 newtons.

    3. Newton’s Third Law: For every action there is an
       equal and opposite reaction.
       a. If object A exerts a force on object B, then
          object B exerts an equal force on object A in
          the opposite direction.
       Click here for video clip
       b. Consequences: Forces always exist in pairs. It
          is impossible for you to push on something
          without it pushing back. Newton’s Third law
          can be used to explain the motion of rockets
          and balloons. As the gases exit the balloon or
          rocket, they push it in the opposite direction.
 B. Motion depends on the observer’s frame of
  C. Speed
     1. a measure of how fast something is moving
     2. the distance traveled in a given amount of time
     3. formula speed = distance
                                             Revised Sunday, July 8, 2007

      4. Sample Problem: A bicyclist rides for 1.5 hours
         from Snellville to downtown Atlanta. He travels 21
         miles. What is his average speed?
          d=21 miles               speed=distance
           t=1.5 hours                      time
                                   speed= 21 miles
                                          1.5 hours
                                   Speed = 14 mi/hr
   D. Velocity
      1. speed in a particular direction
      2. formula: velocity = distance and direction
sheet is Velocity (V) = V0 + at, where V0 = Initial Velocity, a =
Acceleration, and t = Time
      3. Sample Problem: What is the average velocity of
         a commercial jet that travels west from New York
         to Los Angeles (4800 km) in 6.00 hours?
          Velocity = distance
                   = 4800 km
                    6.00 hours
                   = 800 km/hr west
  E. Acceleration
      1. the rate at which velocity changes
      2. formula:               final velocity-initial velocity
                 acceleration =              time

                                            Revised Sunday, July 8, 2007
                                     V  V0 
    or       acceleration =  a             
                                       t 
         from SCIENCE FACTS AND FORMULAS sheet
                                                        V  V0 
Acceleration = Change in Velocity/Time Elapsed  a             
                                                          t 
3. Acceleration occurs if either of these two
   conditions exist.
   a. The speed of an object is changing. It can be
      increasing or decreasing.
 c. The direction of the movement is changing.

          Click here for Video Clip (4 min)

4. Sample Problem: If a car accelerates from 5 m/s to
   15 m/s in 2 seconds, what is the car's average
                                             V  V0 
     V = 15 m/s                          a         
                                               t 
    Vo = 5 m/s                            a= 15 m/s - 5 m/s
     t = 2 sec                                  2 sec
                                          a= 5 m/sec/sec

                                                 Revised Sunday, July 8, 2007

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