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Homework Help: Polar coordinate problems

  1. Sep 23, 2008 #1
    HELP!!!! I just got this assignment over the email a couple hours ago and it's due in the morning and I have no clue how to do these problems! I've spent a few hours trying to figure this stuff out on my own, but I'm down to these last few and I just can't do it. if you can answer one or more, I really appreciate anything AT ALL. I'm sorry I don't have much done already, but I've got a brain block and I'm starting to panic. please help!!!

    2. If a satellite circles the earth at 9000 km from the center, estimate its period T in seconds.

    3. Convert 1/r = C - Dcos(theta) or 1= Cr-Dx into the xy equation of an ellipse.

    5. The Earth takes 365.25 days to go around the sun at at distance d = 93 million miles = 150 million km. find the mass of the sun.
    Last edited: Sep 23, 2008
  2. jcsd
  3. Sep 23, 2008 #2


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    Hi imsoconfused! :smile:

    2. Either compare t with the period of the moon (erm … that's one month! :wink:) …*that only works if you know how far away the moon is, of course.

    Or work out the gravitational force on it, by comparing it with g at the earth's surface … that only works if you know the radius of the earth … and then use centripetal acceleration :smile:
  4. Sep 23, 2008 #3


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    Multiply through by r first. r= [itex]\sqrt{x^2+ y^2} and r cos(theta)= x. You may need to square both sides of an equation to get rid of the square root and get the (standard)equation of an ellipse.

    Problems 2 and 5 are not mathematics problems. They are physics problems and I would be surprised if your book does not have formulas that apply directly.
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