Problem geostationary satellite

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Homework Help Overview

The discussion revolves around determining the height at which a geostationary satellite must be placed above the Earth's surface. The context involves concepts from orbital mechanics and gravitational forces.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the relationship between orbital period, gravitational forces, and circular motion. There are attempts to derive equations related to the satellite's velocity and orbital radius, with some questioning the relevance of height versus velocity.

Discussion Status

Participants are actively engaging with the problem, discussing relevant equations and attempting to connect concepts. Some guidance has been provided regarding substituting variables in equations, indicating a productive direction in the exploration of the problem.

Contextual Notes

There is a mention of the assumption of a circular orbit and the requirement for the satellite's orbital period to match one day, which is crucial for maintaining a geostationary position. Participants express uncertainty about the velocity and its relationship to altitude.

fluidistic
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Homework Statement


At what height (from the ground of the Earth) must be placed a geostationary satellite?


Homework Equations





The Attempt at a Solution

I'm not sure I understand well the question. I guess they are asking for a satellite in such a position that he would not deviate from the point over the ground it is situated. Well, I believe that the height doesn't matter at all and what matters is the velocity you put the satellite in orbit that matters. But the answer of the question is [tex]3.58 \cdot 10^5 \text{km}[/tex]. I have no idea of how to get the solution. Do you have an idea?
 
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They mean that the orbital period is 1 day, so that the satellite is always directly over the same place on Earth.

Also, assume a circular orbit. What equations do you know that apply to:
1. gravity
2. circular motion
 
They mean that the orbital period is 1 day, so that the satellite is always directly over the same place on Earth.

Also, assume a circular orbit. What equations do you know that apply to:
1. gravity
2. circular motion
Hmm... I guess they want me to use [tex]F_c=m_ca_c=m_c\frac{v^2}{r}[/tex]. Also [tex]F_c=\frac{Gm_cM_E}{r^2}[/tex] which led me to conclude that [tex]r=\frac{GM_E}{v^2}[/tex]. But the velocity is unknown so I'm stuck. At last I could calculate it but only in function of the altitude (using the formula [tex]v=\omega r[/tex]) which is precisely what I'm looking for...
 
fluidistic said:
Hmm... I guess they want me to use [tex]F_c=m_ca_c=m_c\frac{v^2}{r}[/tex]. Also [tex]F_c=\frac{Gm_cM_E}{r^2}[/tex] which led me to conclude that [tex]r=\frac{GM_E}{v^2}[/tex]. But the velocity is unknown so I'm stuck. At last I could calculate it but only in function of the altitude (using the formula [tex]v=\omega r[/tex]) which is precisely what I'm looking for...

What is [itex]\omega[/itex] for this satellite?
 
fluidistic said:
[tex]r=\frac{GM_E}{v^2}[/tex]. But the velocity is unknown so I'm stuck. At last I could calculate it but only in function
of the altitude (using the formula [itex]v=\omega r[/itex]) which is precisely what I'm looking for...

You're on the right track. What happens if you substitute [itex]v=\omega r[/itex] into the previous equation here?
 
Oh... Thanks to both! I didn't think about replacing [tex]v[/tex] by [tex]\omega r[/tex]!
 

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