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Minimum height for a satellite to remain over the same geographical point

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F|234K
#1
Feb12-05, 09:39 PM
P: 74
a.)calculate at what height above the earth's surface a satellite must be placed if it is to remain over the same gerographical point on the equator of the earth. b.)what is the velocity of such a satellite?

i have no idea how to do the question, but i know it has to do with these equations:
Fcent.=Fgrav.
m(v^2)/r=GMm/(r^2)

because my book doesn't have answers for this question, i don't know the answer for this question.
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dextercioby
#2
Feb12-05, 09:53 PM
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P: 11,894
That's the equation u need to use,but under an equivalent form.Now find "r" by plugging the correct numerical values...

Daniel.

P.S.HINT:relate angular velocity to tangent velocity...
F|234K
#3
Feb12-05, 10:07 PM
P: 74
dextercioby, can you please show me some work or maybe even tell me the answer. i am stuck becuase i found that there are two variables, "v" and "r", are unknown.

dextercioby
#4
Feb12-05, 10:12 PM
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Minimum height for a satellite to remain over the same geographical point

Yes.[itex] v=\omega r [/itex].And now u have only one variable,namely 'r'...

Daniel.
F|234K
#5
Feb12-05, 10:15 PM
P: 74
sorry for my ignorance, but what is the w(or omega) thing stands for?
dextercioby
#6
Feb12-05, 10:17 PM
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Angular velocity of the Earth's rotation motion.U can find it knowing the period of rotation ("length" of a mean day) and the value of [itex] \pi [/itex],which can be approximated to [itex] 3.14 [/itex]

Daniel.
F|234K
#7
Feb12-05, 10:19 PM
P: 74
i found the answer for part a of my question to be 35870 km, can you please approve it. thanks alot so far.
dextercioby
#8
Feb12-05, 10:28 PM
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It seems correct.However,for point b) u'll need another number,or u can use this 35870Km,but indirectly.

Daniel.
F|234K
#9
Feb12-05, 10:29 PM
P: 74
anyways (i have a feeling that you arn't going to do the question for me), thanks very much dextercioby for your quick response, it helps me a great deal.
F|234K
#10
Feb12-05, 10:29 PM
P: 74
lol....k thanks
dextercioby
#11
Feb12-05, 10:33 PM
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Tell me what number you get for velocity...

Daniel.
F|234K
#12
Feb12-05, 10:38 PM
P: 74
does 3072.6 m/s sounds good?
dextercioby
#13
Feb12-05, 10:40 PM
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Pretty much so.

Daniel.
F|234K
#14
Feb12-05, 10:41 PM
P: 74
k, thanks again.


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