Angular Momentum in a Kepler Orbit

In summary, the satellite rotating at a large distance around planet X has a mass of 1 gram and the planet X has a mass of 1.0 kg. The velocity of the satellite is 10 m/sec and the gravitational constant in this universe is 10**4. The satellite-planet X system has an angular momentum of 1000 m**2/sec. When a second planet, planet Y, is placed next to planet X, the central gravitational source becomes 2.0 kg but the distance and velocity of the satellite remain the same. Therefore, the angular momentum of the system does not increase as neither the momentum nor the radius has changed. However, the satellite will now follow an elliptical trajectory instead of a circular
  • #1
Rapidrain
31
0
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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  • #2
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.
 

Related to Angular Momentum in a Kepler Orbit

1. What is angular momentum in a Kepler orbit?

Angular momentum in a Kepler orbit is a measure of the rotational motion of an object around a central point, such as a planet orbiting a star. It is a conserved quantity, meaning it remains constant unless acted upon by external forces.

2. How is angular momentum calculated in a Kepler orbit?

Angular momentum in a Kepler orbit is calculated by multiplying the mass of the object by its velocity and the distance from the central point. The equation is L = mvr, where L is angular momentum, m is mass, v is velocity, and r is distance.

3. Why is angular momentum important in a Kepler orbit?

Angular momentum is important in a Kepler orbit because it helps determine the shape and stability of the orbit. In a Kepler orbit, the angular momentum remains constant, which allows the object to maintain a stable orbit around the central point.

4. How does angular momentum affect the speed of an object in a Kepler orbit?

Angular momentum affects the speed of an object in a Kepler orbit by keeping it at a constant speed. As the distance from the central point changes, the velocity of the object also changes to maintain a constant angular momentum.

5. Can angular momentum change in a Kepler orbit?

No, angular momentum cannot change in a Kepler orbit unless acted upon by external forces. This is due to the conservation of angular momentum, which states that the total angular momentum of a system remains constant in the absence of external torque.

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