Angular Momentum in a Kepler Orbit

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SUMMARY

The discussion centers on the angular momentum of a satellite in a Kepler orbit around planet X, initially calculated as 1000 m²/sec based on its distance, mass, and velocity. When a second planet, planet Y, is introduced, the total mass of the system increases to 2.0 kg, but the radius and velocity of the satellite remain unchanged. Consequently, the angular momentum of the system does not increase, as neither the momentum nor the radius has changed, although the satellite's trajectory will shift from a circular to an elliptical path.

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Rapidrain
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I got myself here a satellite rotating at a large distance around planet X.

Distance from center of planet X = 100,
mass of the satellite = 1 gram (really small),
mass of planet X = 1.0 kg
velocity of my satellite 10 m/sec
and in this oddball universe the gravitational constant = 10**4

So the satellite-planet X system has an angular momentum of 100 * 10 = 1000 m**2/sec

Now suddenly I place a second planet, planet Y, right next to planet X

mass of planet Y = 1 kg

So at this instant, the central gravitational source is now 2.0 kg but distance is still 100 and velocity of satellite is still 10

My question : has the angular momentum of the system increased?

I'd like to use angular momentum conservation to figure the characteristics of a
satellite / planet / planet trajectory. That's where I'm going with this.
 
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Hi Rapidrain! :smile:
Rapidrain said:
My question : has the angular momentum of the system increased?

Angular momentum = radius "cross" momentum.

Neither the momentum nor the radius has changed, so the angular momentum is also the same.

The satellite will follow an ellipse instead of its original circle.
 

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