Question

question 4 of 10
which statement best describes the motions of the planets around the sun due to gravity?
a. as planets move closer to the sun, they speed up.
b. as planets move closer to the sun, they slow down.
c. as planets move closer to the sun, they neither speed up nor slow down.
d. as planets move closer to the sun, they can speed up or slow down.

Explanation:

According to the law of conservation of angular - momentum, as a planet moves closer to the Sun (decreasing its distance $r$ from the Sun), its orbital speed $v$ must increase to conserve angular - momentum ($L = mvr$, where $m$ is the mass of the planet).

Answer:

A. As planets move closer to the Sun, they speed up.