- #1
lockerman2007
- 9
- 0
I have a question about orbital speed.
Imagine a shuttle moving in an orbit near the Earth surface,
its total energy is "-GMm/2r", so its total energy is directly proportional to -1/r
In order to spiral into another orbit of smaller radius which mean it would have a larger angular speed, the shuttle should increase or decrease its orginal speeed so that it can get into a lower orbital ?
1) increase
As orbital speed = (GM/r)^1/2, speed should increase in order to get a smaller r.
2) decrease
As total energy directly proportional to -1/r,
and total energy = PE + KE
As r decrease, total energy is more negative and KE should decrease
So the speed should decrease.
Are there anything wrong in these two contradicting concept ?
thank you!
Imagine a shuttle moving in an orbit near the Earth surface,
its total energy is "-GMm/2r", so its total energy is directly proportional to -1/r
In order to spiral into another orbit of smaller radius which mean it would have a larger angular speed, the shuttle should increase or decrease its orginal speeed so that it can get into a lower orbital ?
1) increase
As orbital speed = (GM/r)^1/2, speed should increase in order to get a smaller r.
2) decrease
As total energy directly proportional to -1/r,
and total energy = PE + KE
As r decrease, total energy is more negative and KE should decrease
So the speed should decrease.
Are there anything wrong in these two contradicting concept ?
thank you!