This simulation shows a satellite in orbit around a fixed planet. The orbit is calculated using a central inverse square force, that is, standard gravitational force. The input sliders intentionally limit the range of values so that the resulting orbits are closed.

 1 If the mass of the satellite is much less than that of the Earth, how will doubling the satellite's mass affect its motion? Make a prediction, and see how the orbit changes. 2 Start the simulation running with an initial speed of 8 units. The orbit will be elliptical. What is special about the place in the orbit where the satellite reaches its highest speed? What about where the satellite reaches its lowest speed? 3 Start the simulation running with an initial speed of 8 units. The orbit will be elliptical. Arguing only from energy considerations, why must the satellite be moving slowly when it is far away from the Earth? 4 What special condition between the gravitational force and the satellite speed must be met for the orbit to be circular rather than elliptical? Can you produce a circular orbit with the range of parameters available to you? 5 In general are the force vector and the velocity vector perpendicular? What does this tell you about the speed of the satellite? 6 When the Kepler's 2nd Law button is depressed, the radius vector will sweep out areas for one unit of time. How will the areas compare when the planet is close to the sun and is moving quickly to the area when the planet is farther from the sun?