Uses of Ellipses

Date: 04/02/2003 at 20:54:06
From: Rachel
Subject: Uses of Ellipses

I see there are examples of conic sections in daily life on this 
site, but I can't find ellipses. How are ellipses used in real life?

Date: 04/03/2003 at 14:16:13
From: Doctor Douglas
Subject: Re: Uses of Ellipses

Hi, Rachel,

In addition to the astronomy applications mentioned in

   Who uses Ellipses?
   http://mathforum.org/library/drmath/view/54787.html 

Here are some other places where you will find ellipses:

  The shape of a spotlight on a planar surface is in most
  cases an ellipse. In some cases it may be a circle.

  If you cut a cylinder at an angle, you will get elliptical
  sections. This can have important applications in optics 
  (lenses and mirrors can be elliptical in shape), or in the
  kitchen (where one might cut vegetables or sausage along a
  "bias cut" in order to obtain pieces that have the same 
  thickness, but have more surface area exposed.

  Some tanks are in fact elliptical (not circular) in cross 
  section. This gives them a high capacity, but with a 
  lower center-of-gravity, so that they are more stable when
  being transported. And they're shorter, so that they can pass
  under a low bridge. You might see these tanks transporting
  heating oil or gasoline on the highway

  The ellipse is found in art and architecture, and you may be
  familiar with the Ellipse, part of a President's Park South
  (a National Park in Washington, DC, just south of the White 
  House).

  Ellipses (or half-ellipses) are sometimes used as fins, or
  airfoils in structures that move through the air. The 
  elliptical shape reduces drag.

  On a bicycle, you might find a chainwheel (the gear that is 
  connected to the pedal cranks) that is approximately elliptical 
  in shape. Here the difference between the major and minor 
  axes of the ellipse is used to account for differences in the 
  speed and force applied, because your legs push and pull more
  effectively when the pedals are arranged so that one pedal is 
  in front and one is in back, than when the pedals are in the 
  "dead zone" (when one pedal is up and one pedal is down).

- Doctor Douglas, The Math Forum
  http://mathforum.org/dr.math/