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Homework Help: Universal Gravitation and/or Tidal Force

  1. Dec 3, 2016 #1
    1. The problem statement, all variables and given/known data


    The single moon of an Earth-like planet creates tides on the planet that are slowing the planet’s rotation. The planet’s rate of rotation is decreasing at a rate of 7.00 x 10-7 radians/sec/century. The mass of the planet is 6 x 1024 kg, and its diameter is 12,600 km. The radius of the circular orbit of the moon about the planet is 386,000 km. If the moon’s mass is 7.35 x 1022 kg, at what rate is the moon’s distance from the center of the planet increasing? [You may assume that the planet is a uniformly dense sphere.] You must show your work on an attached sheet.

    ∆r/∆t= __________________ km/year

    2. Relevant equations

    Graviational Force/ Universal Graviation
    possible tidal force?

    3. The attempt at a solution

    GMm/r^2 to find acceleration

    then use that acceleration in tidal force equation?
  2. jcsd
  3. Dec 3, 2016 #2

    Filip Larsen

    User Avatar
    Gold Member

    Is there perhaps a quantity that is conserved in this planet-moon system?
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