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Homework Help: Proportion of planetary-period to the distance-from-the-sun

  1. Aug 28, 2011 #1
    1. =The problem statement, all variables and given/known data
    Kepler's law of planetary motion says that the square of the period of a planet (T^2) is proportional to the cube of the distance of the planet from the Sun (r^3). mars is about twice as far from the Sun as Venus. How does the period of Mars compare with the period of Venus?


    2. Relevant equations



    3. The attempt at a solution
    Does this mean that the period of Mars is about twice as long as Venus'?
    T^2=Kr^3
    2T^2=K2r^3
    ???
     
  2. jcsd
  3. Aug 28, 2011 #2

    PeterO

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    Homework Helper

    Short answer , No.

    When you write 2T^2 did you mean 2 * T^2 or did you mean (2T)^2

    Similarly, your K2r^3 : K * 2 * r^3 or K * (2r)^3 or (K * 2 * r)^3
     
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