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Homework Help: Finding out the type of central force given the orbit

  1. Aug 23, 2015 #1

    This is the statement of the problem of AP French's textbook "Newtonian Mechanics".

    1. The problem statement, all variables and given/known data

    The commander of a spaceship that has shut down its engines and is
    coasting near a strange-appearing gas cloud notes that the ship is
    following a circular path that will lead directly into the cloud (see the
    figure). He also deduces from the ship's motion that its angular momentum
    with respect to the cloud is not changing. What attractive (central)
    force could account for such an orbit? (ANSWER : F ~ -1 / r^5)

    2. Relevant equations

    3. The attempt at a solution

    From the information given, angular momentum = m * r^2 * (dtheta / dt) =
    The acceleration of the ship is a combination of tangential and radial
    acceleration, the resultant of which is along the line joining the
    spacecraft and the cloud.

    I don't know where to proceed from here.

    Thank you very much for your help.

    Attached Files:

  2. jcsd
  3. Aug 23, 2015 #2


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    2017 Award

    Staff: Mentor

    This allows you to find velocity as function of radius, which then leads to the potential.
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