Kepler&#x27;s Laws

Kepler's First Law

According to Kepler's first law, planets orbit the sun in the shape of an ________

circle

ellipse

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Explanation

Drawing ellipse

The easiest way to draw an ellipse is to put two tacks in a piece of paper and put a loose loop of a string around them, as shown in the figure below.

$tacks_draw_ellipse.gif$

If the tacks are placed farther apart, how will the shape of the ellipse be changed?

It will be flatter

It will be a circle

It will be a straight line

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Drawing a circle

The easiest way to draw an ellipse is to put two tacks in a piece of paper and put a loose loop of a string around them, as shown in the figure below.

$tacks_draw_ellipse.gif$

What would the positions of the tacks have to be to draw a circle?

Both at opposite sides vertically

Both at opposite sides horizontally

Both at the same point

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State Kepler's first law

Planets orbit the sun in elliptical paths with the sun at one focus of the ellipse

At a planet orbits the sun, a line from the planet to the sun sweeps across equal areas in equal times

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Kepler's second law

As a planet orbits the sun, a line from the planet to the sun sweeps across equal areas in equal times.

True

False

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Does the planet move faster between A and B or between C and D?

$kepler_second_law.gif$

between A and B

between C and D

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What is the shape of the earth's orbit around the sun?

circle

ellipse

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Does the earth move at a constant speed around the sun?

Yes

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