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Calculate angular momentum of a planet only velocities and radii known

  1. Mar 5, 2013 #1
    1. The problem statement, all variables and given/known data
    a planet of mass m orbits a star. The Velocity at point A = 10^4 m/s the Radius at point A = 10^7, Vb = (10^4)/3, Rb = 3*10^7
    Numerically calculate the angular momentum!

    2. Relevant equations

    The main question is how would you calculate the mass?

    3. The attempt at a solution
    L = rmv sintheta or L = IW but you need the mass.
    E =1/2 *mv^2 - mMG/r but you need the mass for this as well. I also tried finding the value of mass by finding it in terms of one of the equations but you need more unknowns
     
    Last edited: Mar 5, 2013
  2. jcsd
  3. Mar 6, 2013 #2
    Angular momentum at a, right? Apply law of conservation of angular momentum. You will notice that mass cancels out. :smile:

    BTW, welcome to PF !!
     
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