Editing Rolling (section)

== Applications ==

Most [[land vehicle]]s use wheels and therefore rolling for displacement. [[Slip (vehicle dynamics)|Slip]] should be kept to a minimum (approximating pure rolling), otherwise loss of control and an accident may result. This may happen when the road is covered in snow, sand, or oil, when taking a turn at high speed or attempting to brake or accelerate suddenly.

One of the most practical applications of rolling objects is the use of [[rolling-element bearing]]s, such as [[ball bearings]], in rotating devices. Made of metal, the rolling elements are usually encased between two rings that can rotate independently of each other. In most mechanisms, the inner ring is attached to a stationary shaft (or axle). Thus, while the inner ring is stationary, the outer ring is free to move with very little [[friction]]. This is the basis for which almost all [[electric motor|motors]] (such as those found in ceiling fans, cars, drills, etc.) rely on to operate. Alternatively, the outer ring may be attached to a fixed support bracket, allowing the inner ring to support an axle, allowing for rotational freedom of an [[axle]]. The amount of friction on the mechanism's parts depends on the quality of the ball bearings and how much lubrication is in the mechanism.

Rolling objects are also frequently used as [[tools]] for [[transportation]]. One of the most basic ways is by placing a (usually flat) object on a series of lined-up rollers, or [[wheel]]s.  The object on the wheels can be moved along them in a straight line, as long as the wheels are continuously replaced in the front (see [[bearing (mechanical)#History|history of bearings]]). This method of primitive transportation is efficient when no other machinery is available. Today, the most practical application of objects on wheels are [[cars]], [[trains]], and other human transportation vehicles.

Rolling is used to apply normal forces to a moving line of contact in various processes, for example in [[Rolling (metalworking)|metalworking]], [[Rotary printing press|printing]], [[Two roll rubber mill|rubber manufacturing]], [[Paint roller|painting]].