Image source: http://www.convocenter.niu.edu/images/renderings/track.jpg
Two semicircles are part of 100 meter turns on a track. If these semicircles
are combined, they would form a circle with circumference of 200 meters. This
information helps builders determine the diameter of this circle, which would
be the distance across the infield of the track.
Image source: http://www.detroit.k12.mi.us/admin/DivEduSer/DeptCurrServices/OffScienceEd/dusp/mathmeasurement2.htm
The circumference of a wheel is the distance that an object will travel in
one revolution. For example, a trundle wheel is a device that measures distance
because its circumference is exactly one meter or one yard.
A hi wheel is a bicycle with one large front wheel and one small rear wheel. The wheels provide examples of how circles are used in real-life. The tire or outside rim of each wheel represents the circumference of the circle.