This simulation shows the energy associated with the Earth as it orbits the Sun. You can try different Earth's - our's is the one with v = 1.0 (roughly times 30000 m/s), the speed needed to go in a circle around the Sun. The others start the same distance we are from the Sun but with different speeds.

The graph shows three plots, all as a function of time. The graph shows the Earth's kinetic energy, the gravitational potential energy of the Earth-Sun system, and the total mechanical energy, which is the sum of the kinetic energy and the gravitational potential energy. Which color goes with which graph? What happens to these energies when the orbit is not circular?