Final answer:
A planet orbits faster at its closest approach to the Sun than at its average distance. Kepler's second law indicates that the orbital speed at the nearest point, or perihelion, would be higher than the average speed of 20 km/s.
Step-by-step explanation:
The student's question concerns a planet's orbital speed at its nearest point to the sun compared to its speed at the average distance. According to Kepler's second law, a planet moves faster when it is closer to the sun in its elliptic orbit than when it is farther away. This law, also known as the law of equal areas, states that a line segment connecting a planet to the Sun sweeps out equal areas during equal intervals of time. Thus, when the planet is at its closest approach, known as perihelion, it travels faster than at any other point in its orbit. However, without the specific details of the planet's orbit (such as its eccentricity), it's impossible to calculate the exact speed at perihelion. What can be said is that it will be greater than the average speed of 20 km/s.