Charles Hakes

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(No Transcript)
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Chapter 1

• Newton
• and Gravity

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Outline

• Notes
• Kepler Review
• Newtons laws
• Gravity
• Tutoring Berndt 610, 640 late afternoons (Katy,
  Shane, Luke)

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Review

• African or European?
• Other favorite answers
• The speed of light.
• I dont know - Im not king!
• My Holy hand grenade blew it up
• 42 (mixing your fiction).
• Im from Oklahoma and have no clue
• for a chimney swallow while hunting mosquitoes.

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Group Exercise

• Assume a comet has a period of 5.2 years, with
  eccentricity very close to 1.

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Group Exercise

• Assume a comet has a period of 5.2 years, with
  eccentricity very close to 1.
• Calculate the semi-major axis.

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Group Exercise

• Assume a comet has a period of 5.2 years, with
  eccentricity very close to 1.
• Calculate the semi-major axis.
• p2 a3
• What is the major axis?
• What is the maximum distance this comet might
  ever get from the Sun?
• Include copy of work in your folder.

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Figure 1.20Isaac Newton (1642-1727)
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An iron weight and a styrofoam ball are dropped
from the same height at the same time.

• Which hits the ground first?
• A) The iron weight
• B) The styrofoam ball
• C) They hit at the same time

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Newtons Laws
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Newtons 1st Law

• If there are no external forces on an object,
  then
• If it is at rest, it will stay that way -
  forever.
• If it is moving, it will keep doing so at
  constant velocity, in a straight line - forever.

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Newtons 1st Law

• Inertia - the natural tendency of an object to
  stay at rest, or remain moving with a constant
  velocity.
• Mass is a quantitative measure of inertia.

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Momentum

• Momentum - the product of mass and velocity.
• momentum mass x velocity
• A concept related to Inertia
• Momentum (both linear and angular) must be
  conserved.

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Which object has the most momentum?

• A) A cruise missile
• B) A ship
• C) A glacier
• D) Need more information

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Which object has the most momentum?

• A - A cruise missile
• 1000 kg
• 100m/s
• B - A ship
• 10 million kg 107 kg
• 10 m/s
• C - A glacier
• 1012 kg
• 1 m/day (10-5 m/s)

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Which object has the most momentum?

• A - A cruise missile
• B - A ship
• C - A glacier

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Angular momentum demonstration
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Angular momentum demonstration

• This is why planets move faster closer to the sun.

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Newtons 2nd Law

• The net force on an object is equal to the mass
  of the object times the acceleration of the
  object
• Fnet m a
• The SI units of force are newtons (N).

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Newtons 2nd Law

• Force - something that is capable of changing an
  objects state of motion (its velocity)
• Fnet - the sum of all forces on an object
• Dynamics - the study of changes in motion and
  what causes those changes

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Newtons 2nd Law

• Fnet m a

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Newtons 3rd Law

• the one hard to believe

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A brick hits a glass window. The brick breaks
the glass, so the magnitude of the force of the
brick on the glass is

• A is greater than the magnitude of the force of
  the glass on the brick
• B is smaller than the magnitude of the force of
  the glass on the brick
• C is equal to the magnitude of the force of the
  glass on the brick
• D none of the preceding

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Newtons 3rd Law

• For every action (force) there is an equal and
  opposite reaction (force).
• Important note - the action-reaction force pairs
  do NOT act on the same object.

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A brick hits a glass window. The brick breaks
the glass, so the magnitude of the force of the
brick on the glass is

• A is greater than the magnitude of the force of
  the glass on the brick
• B is smaller than the magnitude of the force of
  the glass on the brick
• C is equal to the magnitude of the force of the
  glass on the brick
• D none of the preceding

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Gravity
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Figure 1.22Gravity
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Figure 1.24Suns Gravity
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Gravity

• Any object having Mass will exert a gravitational
  force on other massive objects.
• Force is proportional to mass of each object
• F ? M1 M2

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Gravity

• Any object having Mass will exert a gravitational
  force on other massive objects.
• Force is proportional to mass of each object
• Force decreases with the square of the distance
  between the two objects
• F ? M1 M2 / r2

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Figure 1.23Gravitational Force

• Any object having Mass will exert a
  gravitational force on other massive objects.
• F ? M1 M2 / r2

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Gravity

• Any object having Mass will exert a gravitational
  force on other massive objects.
• Force is proportional to mass of each object
• Force decreases with the square of the distance
  between the two objects
• Proportionality constant is G, the universal
  gravitational constant
• G 6.67x10-11 (N m2/kg2)
• F G M1 M2 / r2

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Gravity

• F G M1 M2 / r2

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Newton

• Modification to Keplers 1st Law
• Both the Sun and the planet orbit about the
  center of mass of the system.

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Figure 1.25Orbits
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Newton

• Modification to Keplers 3rd Law
• That math law - updated
• P2 (years) a3 (astronomical units)
  Mtotal(solar units)
• For planets around the Sun, this makes very
  little difference except for (even for) Jupiter
  (0.1 Msun)

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Which mass pair has the greatest gravitational
force between them?

• 1 A 5Msolar mass and a 4Msolar mass separated by
  4 AU.
• 2 A 4Msolar mass and a 3Msolar mass separated by
  3 AU.
• 3 A 3Msolar mass and a 2Msolar mass separated by
  2 AU.
• 4 A 2Msolar mass and a 1Msolar mass separated by
  1 AU.

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Which mass pair has the greatest gravitational
force between them?

• 1 A 5Msolar mass and a 4Msolar mass separated by
  4 AU.
• 2 A 4Msolar mass and a 3Msolar mass separated by
  3 AU.
• 3 A 3Msolar mass and a 2Msolar mass separated by
  2 AU.
• 4 A 2Msolar mass and a 1Msolar mass separated by
  1 AU.

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Group Exercise

• Calculate the force between those two masses.
• A 2Msolar mass and a 1Msolar mass separated by 1
  AU.

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Three Minute Paper

• Write 1-3 sentences.
• What was the most important thing you learned
  today?
• What questions do you still have about todays
  topics?

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Review

• What was the most important thing you learned?
• A circle is actually a special kind of ellipse
  with only one focal point
• A square is to a rectangle as a circle is to an
  ellipse
• The semi-major axis is half of the major axis.
• If the semi-major axis of two bodies is the same,
  they take the same amount of time to orbit.

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Review

• What was the most important thing you learned?
• Planets move faster when closer to the sun
• The closer the focus points, the more like a
  circle the orbit becomes.
• The eccentricity of the ellipse is the ratio of
  the distance between the foci to the length of
  the major axis.

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Review

• Did not get thrown into the abyss. (i.e.
  Remembered Their Monty Python) 3 Other
  memorable answers
• I dont know - Im not king!
• zero???
• My Holy hand grenade blew it up
• Im from Oklahoma and have no clue
• for a chimney swallow while hunting mosquitoes.