Gravitation

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Gravitation
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Developed by Isaac Newton

• One of the inventors of Calculus
• Also contributed to many other areas of Physical
  Science
• Realized connection between things falling on
  earth, and the moon falling in its orbit
• The Law of Universal Gravitation

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Law of Universal Gravitation

• Everything pulls on everything else anything
  with mass (inertial gravitational)
• Pull goes up as mass goes up, and down as the
  distance between objects goes up

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Universal Gravitational Constant

• Turn proportionality into equality need a
  constant
• Measured from nature, Call it G The Universal
  Gravitational Constant

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Scientific Notation and Examples

• 1. Double the mass? Double both masses? Double
  the radius?
• Inverse-Square Law
• 2. In general, what is the acceleration due to
  gravity?
• 3. If the radius of the earth is 6.4 million
  meters, what is the mass?

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Weightlessness

• Depends on what we mean by weight
• Free Fall Still force of gravity acting on you
• But we couldnt get a scale reading of weight if
  in free fall
• Orbiting the earth is like free fall

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Tides

• http//www.ioncmaste.ca/homepage/resources/web_res
  ources/CSA_Astro9/files/multimedia/unit3/tides/tid
  es.html

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Orbits

• Further from Celestial Body (Planet, moon, sun),
  the longer it takes to orbit
• Period - Time to orbit
• Near Earth orbit 90 minutes
• Geosynchronous orbit
• Period is the same as the time for earth to
  rotate (24 hours)
• happens at about 5.5 Earth Radii
• satellite stays directly overhead!

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Keplers Laws

• Planets move in elliptical orbits
• Planet sweeps out equal areas in equal times
• (think about conservation of energy here!)
• http//www.sunsite.ubc.ca/LivingMathematics/V001N0
  1/UBCExamples/Kepler/kepler.html
• Period² Distance³
• Shortcut to PlanetaryOrbits

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• HW 4 (Due 7/17) - Ch. 4 Exercises
  2,6,8,9,11,17,30,33,38 Problem 1

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