Objective 5 Review

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Objective 5 Review

• Quick Physics
• and Energy

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Physics is about Energy and Motion

• How and why do things move?
• Do planets move the same way as a ball that is
  thrown?
• These are the types of questions physics tries to
  answer.

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Potential Energy 2 possibilities

• Gravitational PE -Object lifted to some height
• Elastic PE - A stretched or compressed object
  )(springs

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Gravitational Potential Energy or Will it fall?

• GPE m g h
• m is the mass of the
• object in Kg,
• g is the acceleration
• due to gravity which is
• 9.8 m/s2 on earth and
• h is the height in meters

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Use the formula page! PE mgh

• 41 What is the potential energy of the rock?
• A 59,900 joules
• B 64,600 joules
• C 93,100 joules
• D 121,600 joules

m 95 kg g 9.8 m/s2 h 100 m 95 kg x
9.8 m/s2 x 100 93,100 joules C
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Law of Conservation of Energy

• Energy can change forms, but is never created
  nor destroyed
• Loss in one form gain in an another form
• A falling object speeds up as it falls to the
  ground PE decreases as KE increases. The KE it
  has at impact the PE it had before it fell.

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Example A falling object speeds up as it falls
to the ground

• PE decreases as KE increases, the KE it has at
  impact with the ground is equal to the PE it had
  before it fell

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One type of Energy is Electricity

• Electricity results from electrons moving on a
  path. Current is the moving electrons the Kinetic
  Energy Electricity
• Electricity that is stored is Voltage and that is
  Potential Electrical Energy
• The path is called a circuit. There are 2 types
  of circuits
• Series circuits only one path for the electrons
  
• Parallel circuits more than one path for the
  electrons.

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To figure out which type of circuit. . . .
Parallel Circuit
Series Circuit

• As the path enters one of the resistances (boxes)
  you can see there are more lines in and out in a
  parallel circuit.
• In the Series circuit, you must go on only one
  path through each bulb, so if one burns out, the
  whole string will not light.

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• Which switches, if opened, will
• cause the light bulb to stop glowing?

• Q
• R
• H. S
• J. T

It is the only switch in series to both the
battery and light.
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Ohms LawVoltage Current x Resistance
Standard American Current 110V _at_ 15 or 20 Amps
Power, measured in Watts is P VI
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Voltage Current x Resistance 9V Amperes x
6 ohms or 9V/6ohms

• A 9 V battery is connected to a 6 Ohm resistor.
  How much current will flow through the circuit?
• 54 Amperes
• 15 Amperes
• 3 Amperes
• 1.5 Amperes

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• Which of the following electromagnets would be
  able to pick up the greatest number of paperclips
  if each one was connected to the same battery?

More current from more wraps means a stronger
magnet.
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What is the rule for charges and magnetic poles?
LIKE REPELS LIKE! Since the N pole is marked,
these must both be south.

• In the diagram above, which poles of the magnets
  are interacting?
• A north and a south pole
• Two north poles
• Two south poles

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Another way energy moves is through waves. . .

• Light and sound are two different types of waves.
• Radiation such as light, heat (infrared
  radiation) and radioactivity (x-rays and gamma
  rays) are transverse waves.
• Sound waves are compression waves. They must
  have matter through which to travel.

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Waves

• Transverse Waves vibrate 90o from the direction
  of travel.
• All electromagnetic waves are in this group.
• Visible light and the color spectrum are all
  transverse waves.
• Water ripple waves and microwaves are also of
  this type

• Compression Waves move in the same direction as
  their vibration.
• Sound waves, caused by a disturbance, carried
  through a medium are of this type.
• Some types of earthquakes are also compression
  waves.

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The Electromagnetic Spectrum
Shortest to Longest
Gamma X rays Ultraviolet Visible Infrared
Micro- TV/Radio Radiation
Light Light Radiaion waves Waves
Remember Long Low Slow Long wavelength is
a low frequency and slow velocity.
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• Which of the following waves would have the
  highest pitch and lowest volume?

• Highest pitch means short wavelength
• Lowest volume means smallest amplitude (wave
  height)

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Speed frequency x wavelength

• All radiant energy travels at the same speed.
• 3 x 108 meters/sec
• This is the speed of light through space.
• Radio waves and nuclear energy waves travel at
  the same velocity.

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Speed frequency x wavelength so 343 m/s
512.5 Hz x wavelength

• A sound wave is traveling at 343 m/s and has a
  frequency of 512.5 Hz, what is its wavelength?
• 0.67 m
• 1.5 m
• 169.5 m
• 855.5 m

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Light Spectrum

• Visible light is a small part of the
  electromagnetic spectrum.
• Violet is the shortest wavelength, red the
  longest of visible light.
• As wavelength increases, frequency?

Answer Decreases!
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Waves move, so there can be interference . . .

• When something is an interference, it changes the
  path of movement.
• Constructive means it adds to the waves energy
  or amplitude
• Destructive cancels or decreases the waves
  amplitude

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The diagram shows waves approaching a barrier.
Which pattern will be formed after the waves pass
through the opening in the barrier?


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Quick physics

• Speed or Velocity Distance / Time
• Acceleration Vfinal Vstart / time to change
• Work (joules) Force (Newton) x distance
  (meters)
• Power (watts) Work / time

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Distance / Time Speed so 20m / 40s .5 m/s or
. . . .
5

• A toy car moves 20 m in 40 seconds. What is the
  speed of this car?

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Acceleration Vf Vi / Change in time so . . .
35m/s 15m/s / 10 s 2 m/s/s
5

• An object is moving at 15 m/s and after 10
  seconds the object is moving at 35 m/s. What is
  the acceleration of the object?

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• A young man is standing in line at the grocery
  store holding a 12-pack of Coke weighing 50 N in
  his arms which are 1.5 meters off the ground.
  How much work is he doing?
• 0 Joules
• 6.25 Joules
• 33.3 Joules
• 75 Joules

Work force x distance 50N x 1.5m
Or 75 Joules _
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Power Work/time but nothing here is in
Joules Work force x distance so . . . Power
550N x 5m / 3.5 s 9625 watts

• Lakiesha weighs 550 Newtons runs to the top of
  the 5 m tall staircase in 3.5 seconds. How much
  power is Lakiesha demonstrating?
• 385 Watts
• 559 Watts
• 786 Watts
• 9625 Watts

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Sir Isaac Newton and the 3 Laws of Motion

• Considered one of the foremost physicists,
• Described the motion of all things in a gravity
  and friction free system.
• For each of the next slides, write at least 3
  examples of each law in action. . .

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Newtons FIRST Law

• Law of Inertia
• An object at rest or in motion remains that way
  until acted upon by an unbalanced force.

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Newtons SECOND Law

• Force Mass x Acceleration
• The greater the force on an object in a single
  direction the greater the acceleration in that
  direction will be.

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Newtons THIRD Law

• Law of Action/Reaction
• For every action force there is an equal and
  opposite reaction force.
• Motion is the result of unbalanced forces on the
  same object.

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There are 6 simple machines

• Lever
• 1st Class with the fulcrum in the middle
• 2nd Class with the resistance in the middle
• 3rd Class with the effort in the middle
• To determine the lever classes three, what is in
  the middle spells FRE.

• Pulley, Wheel and Axle, Inclined Plane, Wedge and
  Screw

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Mechanical Advantage and Efficiency, Why Not
100 ?

• Mechanical advantage is how much your force is
  multiplied by the machine
• Efficiency is
• Actual MA/Ideal MA
• Never 100 due to FRICTION
• Almost all energy that is not converted into work
  is converted into heat.