The planet Mars orbits the Sun.
Mars takes 687 days687\text{ days}687 days to orbit the Sun. The average radius of its orbit is 228 million km228\text{ million km}228 million km.
Calculate the average orbital speed of Mars. State your answer to an appropriate number of significant figures and give the unit.
Comets also orbit the Sun.
Name the force that causes planets and comets to orbit the Sun.
Describe the shape of a typical comet's orbit compared to the shape of Mars's orbit.
State where in its orbit a comet travels at its fastest speed, and explain why it travels fastest at this point.
