A student studies the table to identify the factor that determines a planet's orbital velocity, which is the speed at which a planet orbits around a central body. Based on the table, which of the following can the student reasonably conclude?

Question

A.

Distance from the Sun determines a planet's orbital velocity; planets closer to the Sun have a faster orbital velocity.

B.

Rotation period determines a planet's orbital velocity; planets with shorter days have a slower orbital velocity.

C.

Surface gravity of a planet determines its orbital velocity; planets with less gravity have a slower orbital velocity.
D.
Average density determines a planet's orbital velocity; planets with a lower density have a faster orbital velocity.

Answer 1

Based on the principles of celestial mechanics, particularly Kepler's laws of planetary motion, the correct conclusion that can be drawn from the table regarding a planet's orbital velocity is:

A. Distance from the Sun determines a planet's orbital velocity; planets closer to the Sun have a faster orbital velocity.

This conclusion aligns with Kepler's Third Law, which states that the square of a planet's orbital period is directly proportional to the cube of the semi-major axis of its orbit. This means that planets that are closer to the Sun generally have shorter orbital periods and therefore travel faster in their orbits compared to planets that are farther away. The other options provided do not accurately reflect the fundamental physics governing orbital motions.