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This is not homework, I'm 30 years old.

If a moon's velocity is 300 meters/second and it's orbiting a planet whose velocity is 500 meters/second, what is its actual velocity through space, or the equation to find it ?


On average the moon is moving through space at  500m/s. When the moon is orbiting the planet in the direction of the planet's motion the instantaneous velocity of the moon will be equal to the sum of the planet's velocity and the moon's velocity, 800m/s. When it is moving the opposite direction it's speed through space would be equal to the difference in the two speeds, 500-300=200m/s.


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James J. Kovalcin


I am teaching or have taught AP physics B and C [calculus based mechanics & electricity and magnetism] as well as Lab Physics for college bound students. I have a BS in Physics from the University of Pittsburgh and a Master of Arts in Teaching from same. I have been teaching physics for 34 years. I am constantly updating my skills and have a particular interest in modern physics topics.

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