1. How fast do the Planets move? INVESTIGATION What is the order of the planets, from closest to the sun to furthest away? How fast are you travelling right now?

2. What information would a scientist need to investigate the speed of an object? 1. Speed = Distance Time 2. Need to know: The orbital distance of each Planet and the time it takes for the planet to move around the sun. 3. What units should we use to represent speed? What´s appropriate?

3. An Astronomical Unit (AU) One Astronomical Unit is the approximate distance between the Earth and the Sun. 1 AU ≈ 149,600,000 km.

4. Why is 1 AU an approximate distance and not exact? 1.The Earth´s orbit is an ellipse not a perfect circle. 2.There are slight variations in the Earth´s Orbit.

5. Problem that we now face: How do you find the circumference of an ellipse? Formulae do exist but it requires advanced mathematical techniques to derive. Are there any shapes that are slightly more simple than an ellipse that we do know how to find the circumference of?

6. Assumptions in Mathematics Often Mathematicians cannot always find exact answers to problems because it would make the problem too difficult to solve. In these cases, we make simpler assumptions. We can assume that the orbit is circular to decrease the complexity of the problem and find an approximate answer.

7. PlanetMercuryVenusEarthMarsJupiterSaturnUranusNeptune Orbital Radius (AU) 0.380.7211.525.29.4519.230.06 Time to orbit Sun 88 days225 days 365.25 days 687 days 11.9 years 29.45 years 84 years 164.8 years Data Pair Challenge 1: a) The approximate speed of Mercury is 172800 km/h. Use the data to confirm this. b) Change your answer to part a) into km/s and then m/s. Write these answers to 3 significant figures.

8. PlanetMercuryVenusEarthMarsJupiterSaturnUranusNeptune Orbital Radius (AU) 0.380.7211.525.29.4519.230.06 Time to orbit Sun 88 days225 days 365.25 days 687 days 11.9 years 29.45 years 84 years 164.8 years Data (1 AU = 149600000 km) Pair Challenge 2: a)Find the speeds of all the planets in the solar system in km/h, km/s and in m/s. b)Look at the answers you have in km/s. Do you notice anything? Which graph could best show the connection between speed and orbital radius?

9. Topics Discussed Content 1.12, 1.13 - Speed, Distance and Time 6.3 - Circumference of Circles 6.1 - Converting between measurements. 11.3 - Scatter Graphs and Correlation. 1.10 - Significant Figures 1.9 – lead onto Standard form. Skills Simplifying a problem by making assumptions. Ways of displaying data. Appropriate Answers