Editing Rolling (section)

{{Short description|Type of motion which combines translation and rotation with respect to a surface}}
{{Other uses}}
[[File:Rolling animation.gif|right|thumb|The animation illustrates rolling motion of a wheel as a [[Superposition principle|superposition]] of two motions: translation with respect to the surface, and rotation around its own axis.]]
'''Rolling''' is a [[Motion (physics)#Types of motion|type of motion]] that combines [[rotation]] (commonly, of an [[Axial symmetry|axially symmetric]] object) and [[Translation (geometry)|translation]] of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact with each other without [[sliding (motion)|sliding]].

Rolling where there is no sliding is referred to as ''pure rolling''. By definition, there is no sliding when there is a [[frame of reference]] in which all points of contact on the rolling object have the same velocity as their counterparts on the surface on which the object rolls; in particular, for a frame of reference in which the rolling plane is at rest (see animation), the instantaneous velocity of all the points of contact (for instance, a generating line segment of a cylinder) of the rolling object is zero.

In practice, due to small deformations near the contact area, some sliding and energy dissipation occurs. Nevertheless, the resulting [[rolling resistance]] is much lower than [[friction|sliding friction]], and thus, rolling objects typically require much less [[energy]] to be moved than sliding ones. As a result, such objects will more easily move, if they experience a force with a component along the surface, for instance gravity on a tilted surface, wind, pushing, pulling, or torque from an engine. Unlike cylindrical axially symmetric objects, the [[rolling cone motion|rolling motion of a cone]] is such that while rolling on a flat surface, its [[center of gravity]] performs a [[circular motion]], rather than a [[linear motion]]. Rolling objects are not necessarily axially-symmetrical. Two well known non-axially-symmetrical rollers are the [[Reuleaux triangle]] and the [[Reuleaux tetrahedron|Meissner bodies]].  The [[oloid]] and the [[sphericon]] are members of a special family of [[Developable roller|developable rollers]] that [[developable surface|develop]] their entire surface when rolling down a flat plane. Objects with corners, such as [[dice]], roll by successive rotations about the edge or corner which is in contact with the surface. The construction of a specific surface allows even a perfect [[square wheel]] to roll with its centroid at constant height above a reference plane.