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Homework Help: Volume of a sphere without cap

  1. Dec 2, 2013 #1
    1. The problem statement, all variables and given/known data
    A solid sphere of radius R has a spherical cap, defined by the cone theta = alpha, removed from its "north pole". Determine the volume of the sphere without cap.

    2. Relevant equations

    3. The attempt at a solution
    Well obviously, the volume would be volume of sphere - volume of cap.
    I am able to derive the volume of the sphere and obtain the formula 4(pi)r^3/3, but I am not sure about the volume of the cap. Is this the same cap that is talked about? http://en.wikipedia.org/wiki/Spherical_cap
    If so, the volume would (pi)h^2/3(3r-h), and the answer could be found by subtracting the two quantities. My class focuses on deriving the quantities though, and I am confused and want to understand on where to start for deriving the volume of the cap.
  2. jcsd
  3. Dec 2, 2013 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    what does "theta=alpha" mean?
    Do you mean that the apex angle of the cone is ##\alpha##? The half-angle at the apex?

    The cap is the regeon described in the wikipedia entry you linked to - yes.
    Why not use the same method for the volume of the cap that you used for the volume of the sphere?

    For that matter - why not do it in one go by carefully choosing your limits of integration?
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