Ellipses

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Ellipses
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Aim What are the shapes of the planets orbits
around the sun?
I. Revolution the movement of one body around
another body. An orbit is the path taken by one
body as it revolves around the other body.
A. Focus a fixed, central point. A circle has
one focus.
B. Ellipse A flattened circular path that has
two foci (fixed points).
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C. Eccentricity the roundness of a circle

• Eccentricity distance between foci
• length of major axis

Major axis
Focii
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II. Orbital Velocity time per distance of a
planets path around the sun.
A. A planets orbital velocity changes throughout
its orbit.
Perihelion
Sun
Earth
Aphelion
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Effects of changing
distance between focii
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1. A planets orbital velocity is greatest when
it is at its perihelion (point in orbit where a
planet is closest to the sun).
2. A planets orbital velocity is least when it
is at its aphelion (point in orbit where a planet
is furthest from the sun).