Satellite motion and Moment of Momentum

AI Thread Summary
The discussion revolves around solving a problem related to satellite motion and moment of momentum. The user attempts to apply the cross product of position and velocity vectors to establish relationships between different orbits, indicating that the velocity ratio is 7. They express difficulty in progressing further, especially when incorporating energy relations that involve the gravitational constant and the mass of the planet. Participants suggest focusing on centripetal acceleration and the gravitational forces in the orbits, as well as emphasizing the importance of angular momentum. The conversation highlights the need for a clearer approach to the problem using established physics principles.
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Homework Statement



http://img194.imageshack.us/img194/4638/001ofa.jpg

Homework Equations



Not too sure to be honest.

The Attempt at a Solution



Well, r1 cross product m v1 = r2 cross m v2
But, there is a force applied so I have to take that into account.
I was thinking,
The moment of momentum after the thrust = Moment of momentum when it first enters the second orbit

r1 m v1 = r1 m v2

gives
v2/v1 = 7
But I am not being able to take that any further.

I'm trying to use energy relations but it gives me an equation in terms of GM (gravitational constant and mass of planet).

I have no idea where to begin. Maybe you guys could point me to the right direction?
 
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pal, where's your question ?
 
http://img194.imageshack.us/img194/4638/001ofa.jpg

Can the image not be seen? I've scanned the question and posted it there...
I got rid of it and now there's a link.
 
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Hint: what is the equation of motion for a satellite in a circular orbit?
 
___ said:

Homework Statement



[PLAIN]http://img194.imageshack.us/img194/4638/001ofa.jpg

Homework Equations



Not too sure to be honest.

The Attempt at a Solution



Well, r1 cross product m v1 = r2 cross m v2
But, there is a force applied so I have to take that into account.
I was thinking,
The moment of momentum after the thrust = Moment of momentum when it first enters the second orbit

r1 m v1 = r1 m v2

gives
v2/v1 = 7
But I am not being able to take that any further.

I'm trying to use energy relations but it gives me an equation in terms of GM (gravitational constant and mass of planet).

I have no idea where to begin. Maybe you guys could point me to the right direction?

Use the image feature to get your image to show.
The literal string of characters I used was:
\text{[PLAIN]http://img194.imageshack.us/img194/4638/001ofa.jpg }
 
Last edited by a moderator:
___ said:

The Attempt at a Solution



Well, r1 cross product m v1 = r2 cross m v2
But, there is a force applied so I have to take that into account.
I was thinking,
The moment of momentum after the thrust = Moment of momentum when it first enters the second orbit

r1 m v1 = r1 m v2

gives
v2/v1 = 7
But I am not being able to take that any further.

I'm trying to use energy relations but it gives me an equation in terms of GM (gravitational constant and mass of planet).

I have no idea where to begin. Maybe you guys could point me to the right direction?
What is the centripetal acceleration in each of the circular orbits. How does the centripetal force supplied the planet's gravity compare for the two circular orbits.

Yes, using angular momentum (moment of momentum) may be helpful.

I think using energy relations is a very good idea. Yes, of course it will include GM. That should not be a problem.

You should be able to answer part (d) first. That may be the biggest help of all.


 
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