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Planetary Motion 20.4

Sept 3, 2015 Planetary Motion II 20.4 pgs 630-633


What is Kepler’s 1st Law?

All planets travel around the sun in an elliptical orbit.


What is Kepler’s 2nd Law?

A Planet move through the orbit faster when it is closer to the sun.


When it is further away it moves slower.


At point A, a planet moves faster. At point B the planet will move slower.


What is Kepler’s 3rd Law?

Planets farther away from the sun, take longer to orbit the sun.


How does gravity and inertia

Gravity is a force that pulls. Inertia keeps objects moving in a straight line.

Work together?

These forces work together to form the orbit. Without inertia, all objects


Will crash into the sun. Without gravity, all objects will go out into the




What is the retrograde rotation

Mars appears to move backwards when it moves around the sun.

Of Mars and the outer planets

Because Earth is closer to the sun in its orbit. I appear that Mars is

From Earth’s perspective?

Making a looping motion.


An image of the retrograde motions of Mars and Uranus in 2003, created by superimposing images taken on 29 different dates


Summary (Write summary in three or four sentences at the end of all notes pages on the topic)


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