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Homework Help: How would you calculate the length of a year on a planet?

  1. Oct 29, 2015 #1
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    1. The problem statement, all variables and given/known data
    How would you calculate the length of a year in Earth years on a hypothetical planet? (given the mass + radius of the planet)

    I understand Kelper's law is used somehow, but is orbital velocity needed?
  2. jcsd
  3. Oct 29, 2015 #2

    rude man

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    Try Law #3, "The Law of the Periods".
    The radius of the planet is a no-count. So is the mass.
  4. Oct 30, 2015 #3
    You can start with: gravitational attraction = centripetal force
    G M m / R^2 = m v^2 / R
    I assume that by radius is meant the radius (mean) of the planet's orbit.
    Note that the period can then be calculated in terms of v and R.
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