Video Transcript
Earth orbits the Sun at a distance of 1.50 times 10 to the eight kilometers. Venus orbits the Sun at a distance of 1.08 times 10 to the eight kilometers. Which planet is moving faster around the Sun?
Let’s begin by sketching a diagram of Earth and Venus in orbit around the Sun. Their orbits are almost perfectly circular. And we know that Earth is a little farther away from the Sun than Venus is. For circular orbits like we have here, the distance from the center of the Sun to a planet’s orbital path is described as its orbital radius. And in this question, we’ve been asked to compare the planet’s orbital speeds and determine which one is moving faster.
We can say that there is an inverse relationship between orbital radius and orbital speed. This is because as one quantity increases, the other decreases. Therefore, a greater orbital radius means a lower orbital speed. Likewise, a planet with a smaller orbital radius moves at a greater speed. Because of this, we know that the faster moving planet must have a smaller orbital radius.
Venus is closer to the Sun than Earth is. So we know that Venus moves faster around the Sun.
