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Football Shape
Name: Robbie
Status: student
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
What is the 3-D shape of a football called? A soccer
ball is circular and called a sphere. A football is an ellipse but what
do you call the 3-D shape called?
Replies:
A football is not really an ellipse. The equation of the projection onto
the x/y plane of an ellipse of revolution is (x/a)^2 +(x/b)^2 = 1. where 'a'
and 'b' are the semi-major and semi-minor axes, respectively. The foot ball
is too "pointed" on the ends to be an ellipse according to the definition
above. The general name for objects that have an axis of symmetry, like a
football ignoring the sewing and the laces, is an oval of revolution.
There are methods for generating analytical equations of such geometric
figures, but space does not permit that discussion in this forum.
Vince Calder
Robbie,
The three-dimensional figure that best fits a football is an ellipsoid. An
ellipsoid is formed by rotating an ellipse around one of its two axes. You
can get something like a football or something like a flying saucer,
depending on which axis you choose.
Dr. Ken Mellendorf
Illinois Central College
An Americal football is a prolate spheroid. This means that its axis of
symmetry is longer than its other axes. Am M&M candy, on the other hand, is
an oblate spheroid. Its axis of symmetry is shorter than its other axes.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
See http://mathworld.wolfram.com/Lemon.html
Thanks to David H.
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Update: June 2012
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