Answer:
The planet moves faster when closer to the Sun and slower when it is far from it
Explanation:
The law of planetary motion that answers to this question is the 2nd Kepler's law, which states that:
"A line connecting the centre of the Sun to the centre of each planet sweeps out equal areas in equal time intervals"
In order to understand what are the consequence of this law to the orbital velocity of each planet, we have to keep in mind that planets have an elliptical orbit, with the Sun occupying one of the two focii (Kepler's 1st law).
As a result, the planet at some point of the orbit is farther from the Sun, while at some point is closer to it.
Given to Kepler's second law, this means that when the planet is farther, the orbital velocity must be lower (because the line connecting the planet to the Sun is longer, so it can cover the same area moving less), while when the planet is closer to the Sun, the orbital velocity must be higher (because the line connecting the planet to the Sun is shorter, so it will cover less area if moving at the same speed.
