# kepler’s law

Procedure: Part I – Kepler’s 1st Law

1. The major axis in the drawing below is line _______

2. The minor axis in the drawing below is line _______

3. Focal points 1 and 2 have been indicated for you in the drawing.

4. You are now going to calculate how out of round your ellipse is. This is the ellipse’s squish factor or better knows as its eccentricity.

Using your ruler, measure the distance between the focal points in centimeters.

Dist. between foci = ________________

Using your ruler, measure the length of the major axis in centimeters.

Major axis = ______________

5. Calculate the eccentricity of the orbit by using the following equation.

Distance between focal points

Ecc. =

Major Axis

Ecc. = ______________

6. You will now see how different eccentricities will change the shape of the ellipse.

The following diagrams are courtesy of Nebraska Astronomy Applet Project.

7. The following display shows an orbit with an eccentricity of approximately 0.

Q1. What shape is this orbit?

8. The following display shows an orbit with an eccentricity of approximately .17 the eccentricity of Earth’s orbit.

9. The following display shows an orbit with an eccentricity of approximately .25, the eccentricity of Pluto’s orbit, the most eccentric of all the planets.

10. The following display shows an orbit with an eccentricity of approximately .7, the eccentricity of a repeating comet’s orbit.

Q2. What pattern do you see between the eccentricity and the shape of the orbit?

Procedure: Part II – Kepler’s 2nd Law

1. The following display shows an orbit with an eccentricity of approximately 0.

Q3. Since this is a circle how do the areas of colored compare?

2. The following display shows an orbit with an eccentricity to approximately your answer in step 5

.

Q4. Do these colored triangles look to be of equal area?

3. Using the data tables in the diagram below.

Q5. What is the sweep area of each?

________________ square A.U.

Q6. Using your answer from question 5 above, how do each of these areas compare?

Q7. The time the planet took to form the base of each colored triangle is called the sweep duration which is:

_______________ years

Summary:

As a planet moves around the sun it will sweep out equal _________ in equal _________ .