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Homework Help: Semi major axis

  1. May 14, 2010 #1
    my question is.......... the semimajor axis of the orbit of jupiter is 7.8*108.
    If an asteroid has an orbital period half of that of jupiter what is the semi major axis?

    All i did was times 7.8*108 by 1/2 and got 3.9*108.

    Seems to simple!!??

    any comments much appreciated
  2. jcsd
  3. May 14, 2010 #2

    D H

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    What does Kepler's third law say?
  4. May 14, 2010 #3
    that the square of the orbital period is propotional to the square of the semi major axis.

    im unsure of how to apply this though.

    I believe T2/a3=K to be relivent but as i only know that the semi major of the sun and jupiter is 7.8*108 I am confused what to do next
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