Law of universal gravitation

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Law of universal gravitation
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• Misconceptions about falling objects video
• http//www.youtube.com/watch?v_mCC-68LyZM
  (Veritasium)
• Video from the universe beginning
• http//www.youtube.com/watch?vDmUiCweDic4 (TED)

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Lesson 1 Focus questions

• What do we mean when we say gravity is always an
  attractive force?
• What is G?
• Why is the law of universal gravitation called an
  inverse square law
• Is gravity a field or contact force?
• Handout Planetary Data Sheet (NASA)

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Notes- Law of Universal Gravitation

• Any two masses are gravitationally attracted to
  each other
• Newtons Law of Universal gravitation
• Fg G m1 m2 G
  6.673x10-11Nm2
• r2
  kg2
• r is the distance from the center of one object
  to the center of the other

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Notes- Law of universal grav.

• As the distance r between the objects increase
  what happens to the force? ________
• If mass increases and the distance between the
  objects stays the same, how does this affect the
  force? ____________
• Sooooo..
• the closer the objects the ________
• the more massive the objects the ______

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Notes- Law of universal grav.

• As the distance r between the objects increase
  what happens to the force? decreases
• If mass increases and the distance between the
  objects stays the same, how does this affect the
  force? increases
• Sooooo..
• the closer the objects the greater the force
• the more massive the objects the the greater the
  force

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Notes Example

• What is the gravitational force of attraction
  between Pluto and the sun?
• Note masspluto 1.309 x 1022 kg
• mass sun 1.98x1030 kg
• r pluto-sun 5.914x 109 m

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Applying Newtons Law of Universal gravitation-
example

• Two students are 5.0m apart. One has a mass of
  35kg, the other has a mass of 70 kg. What is the
  force of gravity from one student on the other?

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Now you try

• Calculate gravity on the surface of the Earth.

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Circular Motion- The Big Idea

• Big idea to maintain circular motion requires a
  force directed inward. This is caused by gravity
  (for planets)

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Putting it all togher!!!

• From the last unit we learned to maintain
  circular motion you need an inward directed force
  . IN THE CASE OF A PLANET ORBITING THE SUN THAT
  INWARD DIRECTED FORCE IS THE FORCE OF
  GRAVITY!!!!!!!
• orbital motion Fc Fg
• So mv2 Gm1m2
• 
  r r2

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(No Transcript)
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Worksheet

• In small groups work on the worksheet showing
  your steps to proper problem solving, boxing
  answers and including appropriate units!