Read and follow ALL directions carefully!
1)Gather materials: Cardboard, string, ruler, two thumbtacks and a clean sheet of paper
2)Fold the paper in thirds, then flatten it out. The folds divide the paper into spaces where you will draw and compare 3 ellipses. Measure and mark two dots 1.5 cm apart in the center of the top third of the paper. Measure and mark two dots 2.5 cm apart in the center of the middle third of the paper. Measure and mark two dots 3.5 cm apart in the center of the bottom third of the paper.
3)Put the paper over the cardboard and push the thumbtack into one set of points. Push the pins in all the way. These are the foci of the ellipse. Put the string around the thumbtacks and use the pencil to draw an ellipse by keeping the string taunt. See figure 4.
4)Repeat step three for the other two sets of foci. It is okay if an ellipse goes off the paper at the top and bottom, as long as the major axis is on the paper. Put some scrap paper down so that you don’t draw on the desk.
5)Use a ruler to neatly draw and label the major axis on each ellipse.
6)Label the first ellipse “Planet A” and label the left foci the Sun.
7)Label the second ellipse “Planet B” and label the right foci the Sun.
8)Label the third ellipse “ Planet C” and label either foci the Sun. It does not matter which foci you choose.
9)Place a red “x” on each ellipse where the planet would be at perihelion.
10)Clean up your materials. Place the push pins and the string back in the bag. Put the bag on top of the foam board and put the pencils neatly to the left. Before you begin the questions quietly go tell Ms. Gill in these exact words, “Your impeccable sense of style is light years ahead of other teachers.” Then, complete the questions.
Questions:
- Calculate the eccentricity ofeach ellipse, round your answer to the nearest thousandth. Show your work and the formula.
Planet A / Planet B / Planet C
2. Which planet has the most circular orbit? ______Which planet has the most elliptical orbit?______
3. Compare the eccentricity of Planet B's orbit to the eccentricity of Venus.
______
4. What will happen to the value eccentricity of Planet C's orbit if you moved the push pins out to 6 cm?
______
5. State the relationship between eccentricity and shape of a planets orbit. ______
6. Look up the following information in your textbook and fill in the blanks.
a) Earth is at perihelion on ______; on that date, Earth is approximately ______km from the Sun. In the Northern Hemisphere the Season is ______
b) Earth is at aphelion on ______; on that date, Earth is approximately ______km from the Sun. In the Northern Hemisphere the Season is ______
7) Based on your understanding of Kepler's First Law, explain why the distance from a planet to the Sun is typically given as a mean distance (average) ? ______