Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The widest point on an ellipsoid

  1. Apr 2, 2008 #1
    I am looking for a term to describe the widest part of an ellipsoid. However this ellipsoid is irregularly shaped because it's a wine glass. As the glass goes up from the stem it continues to widen and then toward the brim it begins to narrow again just a little. So basically it is an ellipsoid which is cut off at one of the ends of it's Z-axis. I was wondering of anyone knew the name of the point where it begins to narrow again.
     
  2. jcsd
  3. Apr 2, 2008 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    there not a single point where the ellipsoid starts to "narrow" again- its a whole circle around the ellipsoid. If you write the ellipsoid in the standard form
    [tex]\frac{x^2}{a^2}+ \frac{y^2}{a^2}+ \frac{z^2}{b^2}= 1[/itex]
    assuming that the z axis points toward the stem of the wind glass, then the base of the bowl is at (0, 0, -b) and the bowl starts to narrow at z= 0, where the circle around the bowl is [tex]x^2+ y^2= a^2[/itex].
     
  4. Apr 3, 2008 #3

    CRGreathouse

    User Avatar
    Science Advisor
    Homework Helper

    HallsofIvy describes it well, but I think you're looking for a term, not an equation. I'd say it's the circle along the major axis of the spheroid (ellipse).
     
  5. Apr 4, 2008 #4

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    The "major axis" is a line- you can't have "circle around" it. Perhaps you meant a circle in the plane perpendicular to the major axis, passing through the center of the ellipsoid.
     
  6. Apr 4, 2008 #5

    CRGreathouse

    User Avatar
    Science Advisor
    Homework Helper

    Yes, that. :)
     
  7. Apr 4, 2008 #6
    In a given ellipsoid, the circle in a plane perpendicular to the major axis and passing through the center has the greatest radius. Can this circle be said to represent the equator of the ellipsoid, or does that term only apply to celestial bodies?
     
    Last edited: Apr 4, 2008
  8. Apr 4, 2008 #7
    You're right Ynaught, I looked it up and equator is the correct term and can be applied to more than just celestial bodies.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?