Could you make your marble orbit like this

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Could you make your marble orbit like this?
Engagement
2
An oval?no no a racetrack...wait! A silly putty
container painted white!
Engagement

• How can we describe this shape?
• What is the mathematical name of this shape?

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Ellipses
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Major Axis
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Major Axis
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Major Axis ... size!
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Semi-major axis
a
a
a
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a half the longest diameter
a
a
a
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Two foci
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distance between foci
?
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c distance from center to focus
c?
c
c
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eccentricity c a
a
a
c0
c
a
c
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eccentricity ... shape!
a
a
c0
c
a
c
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Sum of distances to foci
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remains constant ...
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remains constant ...
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remains constant ...
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remains constant ...
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remains constant ...
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remains constant ...
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and equals 2a (major axis )
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Drawing an ellipse
pencil
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Drawing an ellipse
pencil
string
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Drawing an ellipse
pencil
string
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keep the string taut
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Just trace it on around.
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Just trace it on around.
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Just trace it on around.
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Just trace it on around.