Cycloid Cycloid A cycloid is the curve traced by a point on the rim of a circular wheel as the wheel rolls along a straight line without slipping. A cycloid is a specific form of trochoid and is an example of a roulette, a curve generated by a curve rolling on another curve. The cycloid, with the cusps pointing upward, is the curve of fastest descent under constant gravity, and is also the form of a curve for which the period of an object in descent on the curve does not depend on the object's starting position. The cycloid has been
The Rolling Bridge to this bridge. At present, this curling bridge is the only one of its type known to be in existence. Traditional use of the term "rolling bridge" dates from at least the Victorian era, and is used to describe a type of retractable drawbridge used to span a ditch or moat surrounding a fortification. That type of bridge is not hinged, and remains horizontal when it is rolled inside the gates of a fort. Modern versions are called retractable bridges or "thrust bridges". One particular version of the rolling bridge type was known as the Guthrie rolling bridge, examples of