Generally the speed of planets is given to us in miles per second. Find out about the orbital speeds of the planets in miles per hour with help from an educational professional in this free video clip.

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Generally the speed of planets is given to us in miles per second. Find out about the orbital speeds of the planets in miles per hour with help from an educational professional in this free video clip.

Part of the Video Series: Moons & Planets

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Hi, my name is Eylene Pirez, and I'm an astrophysicist, and this is the orbital speed of a planet in miles-per-hour. So generally when we read, or when we Google this speed of the planets, they give it to us in meters-per-second, and that's because generally in physics we use SI units. A quick way to always calculate this is to use this formula, and it's the orbital speed square is equal to the gravitational constant g, the central mass of the solar system which would be the sun, and I will denote it with a circle and a dot in the center, divided by the distance of the planet to that sun. So, generally let's say Mercury is 50,000 meters-per-second, that's is our real speed. So if we want that in miles-per-hour, the best way to do this is to actually come up with conversion factors. So the first thing that we need to know is how many meters are in a mile, and how many seconds are in an hour so we can get to the units that we desire. So the best way to do this is to come up with a fraction in order to cancel units. So let's say if I know that there is 1609 meters in one mile, the way output would be a fraction because they're equivalent, and I'll be able to cancel meters and leave the mile. And then the other thing that I need to cancel is the seconds. So I know that there's 3,600 seconds in one hour, which is the unit that I want. If you multiply this all out, you'll end up with about 110,000 miles-an-hour, and that will be the orbital speed of mercury. And here is the rest of them. So this is 110,000 miles-an-hour, this one is 78,350, this one is 66,630, and for Mars is 54,060, Jupiter is 29,240, this one is 21,640, Uranus is 15,290, and Neptune is 10,700. And all of these are in miles-per-hour. So you can try to plug in the distances and calculate it yourself if you want to, but this is the orbital speed of the planets in miles-per-hour. My name is Eylene Pirez, and I'm an astrophysicist.