As indicated in Figure on the next page, fix the graph paper on a cardboard using pins. Get about 15 centimeters (cm) long srting and tie a knot of the open ends to make a loop. Draw first ellipse by separating two push pins about 3 cm; using the string loop and pencil as shown in the picture. Label it ellipse 1. Draw second ellipse by separating the two push pins about 6 cm. Label it ellipse 2. Draw semimajor axis. Mark pin pricks as f1 and f2 to represent the foci of the ellipse as shown in the sketch. Measure the distance between the foci and record it as B in the blank space below with proper unit. Now measure the distance between f1 and perihelion and represent it as A. Repeat this for ellipse 2 as well. By using the definition of the eccentricity we learnt in class, one can write eccentricity as: 2 B e B A ? ? Now calculate the eccentricity of each ellipse by using the above formula and the recorded values of B and A. Ellipse 1: B = _______ A = _________ ; eccentricity of 1 (e1) = -------- Ellipse 2: B = _______ A = _________ ; eccentricity of 2 (e2) = -------- Do not fill in the space above and turn in the page. Copy these calculation steps in the data and calculation section of your lab report that you are writing by using general instructions for all lab reports. Also staple your drawing in the back of your report. It is also part of your data. In the Conclusion and Analysis section of your report include following and more. How does the eccentricity and flatness are related? The eccentricity of planets' orbit varies from about 0.0097 to 0.20565. Which ellipse you drew is closest to the orbit of the planets. What is the eccentricity of the Earth's orbit? Is it more or less flat than one of the ellipse you drew? What are the possible sources of error? How can they be minimized? What did you learn from this exercise?

u u l. 1 A 4 1 a separating the two push pins about 6 cm. Label it ellipse 2. Draw semimajor axis. Mark pin pricks as f1 and f2 to represent the foci of the ellipse as shown in the sketch. Measure the distance between the foci and record it as B in the blank space below with proper unit. Now measure the distance between f1 and perihelion and represent it as A. Repeat this for ellipse 2 as well. By using the denition of the eccentricity we learnt in class, . . . B one can write eccentr1c1ty as: e = B + 2A Now calculate the eccentricity of each ellipse by using the above formula and the recorded values of B and A