Many of the planets in the solar system have orbits of similar shapes, but they orbit at very different speeds. Why do the planets orbit at different speeds?

Question

Many of the planets in the solar system have orbits of similar shapes, but they orbit at very different speeds. Why do the planets orbit at different speeds?

A.

Planets are kept in their orbits by tension force, which is affected by the atmospheric pressure of a planet.
B.

Planets are kept in their orbits by electromagnetic force, which is affected by the diameter of a planet.
C.

Planets are kept in their orbits by friction, which is affected by the temperature of a planet.
D.

Planets are kept in their orbits by gravity, which is affected by the mass of a planet.

Answer 1

D. Planets are kept in their orbits by gravity, which is affected by the mass of a planet. The larger the mass of a planet, the stronger the gravitational force pulling it towards the sun, resulting in faster orbital speeds. This is why planets like Mercury, which is closer to the sun and has a smaller mass, orbits at a faster speed compared to planets like Neptune, which is further away and has a larger mass.