Extra Credit

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Extra Credit

• Poster presentation (full poster)
• Pick a topic projectile motion or Newtons
  laws.
• Must include
• Picture
• Title
• 10 vocabulary words
• 3 higher level questions and answers
• 5 key points
• Work cited

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How will this extra credit help?

• Replace a minor grade
• Or
• Up to 20 points added to a major grade

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When is this due?

• No later than Wednesday the 5th at 5pm.

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The Nature of Energy
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Energy

• The ability to cause change or the ability to do
  work
• Unit for Energy Joule (J)

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Energy

• Two main types of energy
• Kinetic
• Potential
• Other types of energy include
• Thermal
• Light
• Sound
• Electrical
• Chemical
• Nuclear

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Kinetic energy

• Energy in the form of motion
• Kinetic energy ½ x mass x velocity2
• KE ½mv2

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Potential Energy

• Energy stored in a motionless object, giving it
  the potential to cause change

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3 Types of Potential Energy

• Elastic Potential Energy Energy stored by
  things that stretch or compress (springs,
  elastic, rubberbands)

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• Chemical Potential Energy - energy stored in
  chemical bonds between atoms (Snickers bar, food,
  even gasoline)

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• Gravitational Potential Energy energy stored by
  things that are above Earth (book sitting on
  shelf, person standing on a cliff, rollercoaster
  perched at the top of a hill)

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Gravitational Potential Energy

• GPE mass x acceleration due to gravity x height
• GPE mgh

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Law of Conservation of Energy

• Energy cannot be created or destroyed, only
  change form.
• MEi MEf or
• KEi PEi KEf PEf

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Law of Conservation of Energy (example)

• Fuels store energy in the form of chemical
  potential energy.
• This energy is transformed into heat energy,
  which is then transformed into kinetic energy.

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• Ex 1gasoline put into your car (chem. Pot.
  Energy)it is heated/combusted and a chemical
  reaction occurs so that the energy stored in the
  bonds can be released in the form of heat. Then,
  the heat energy is used to move parts like
  pistons, etc (kinetic energy) which eventually
  moves your car!

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• Ex 2Candy bar has chemical potential energyyou
  eat ityour body digests it, meaning it breaks
  down the food even breaking the bonds and
  releasing energy. Your body uses the energy to
  move (kinetic energy)!

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Example Problem 1

• A 50 kg boy and his 100 kg father went jogging.
  Both ran at a rate of 5 m/s. Who had more
  kinetic energy? Show your work and explain.

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Example Problem - answer

• KE ½mv2
• Boy
• KE ½(50 kg)(5 m/s)2
• KE 625 J
• Dad
• KE ½(100 kg)(5 m/s)2
• KE 1250 J
• Dad had more Kinetic energy because his mass was
  greater.

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Example Problem 2

• What is the potential energy of a 10 N book that
  is placed on a shelf that is 2.5 meters high?

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Example Problem 2 - answer

• GPE mgh
• GPE (10 N) (2.5m)
• GPE 25 J
• Remember that weight mg and that the force
  provided is weight.
• NOTE you may want to change your variable for
  weight to Fg.