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# Rolling

Rolling is a combination of rotation (of a radially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that the two are in contact with each other without sliding. This is achieved by a rotational speed at the cylinder or circle of contact which is equal to the translational speed. Rolling of a round object typically requires less energy than sliding, therefore such an object will more easily move, if it experiences a force with a component along the surface, for instance gravity on a tilted surface; wind; pushing; pulling; an engine. Objects with corners, such as dice, roll by successive rotations about the edge or corner which is in contact with the surface.

One of the most practical applications of rolling objects is the use of ball bearings in rotating devices. Made of a smooth metal substance, the spherical bearings 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 motors (such as those found in ceiling fans, cars, drills, etc) rely on to operate. 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 wheels. 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 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 friction
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* Tumbling (gymnastics)

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• Rolling — Roll ing, a. 1. Rotating on an axis, or moving along a surface by rotation; turning over and over as if on an axis or a pivot; as, a rolling wheel or ball. [1913 Webster] 2. Moving on wheels or rollers, or as if on wheels or rollers; as, a… …   The Collaborative International Dictionary of English

• rolling in — (something) having a lot of money or wealth. The business is rolling in cash. It s pretty obvious that these people aren t rolling in luxury. Usage notes: sometimes used in the form rolling in it very rich: Mary s new husband is rolling in it …   New idioms dictionary

• Rolling — ist der Familienname folgender Personen: Danny Harold Rolling (1954 2006), US amerikanischer Serienmörder und Hingerichteter Rolling ist ebenfalls der Name folgender Ortschaft: Rolling (Wisconsin), eine Ortschaft im Langlade County, im US… …   Deutsch Wikipedia

• rolling — UK US /ˈrəʊlɪŋ/ adjective [before noun] ► used to describe something that is done in stages over a long period: »He prepared a five year rolling plan for equipment maintenance …   Financial and business terms

• rolling — adjective (of land) extend in gentle undulations. → roll rolling adjective steady and continuous: → roll …   English new terms dictionary

• rolling — [rōl′iŋ] adj. 1. that rolls (in various senses); specif., rotating or revolving, recurring, swaying, surging, resounding, trilling, etc. 2. having or forming curves or waves [rolling hills] n. the action, motion, or sound of something that rolls… …   English World dictionary

• Rolling — Rolling. См. Прокатка. (Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО Профессионал , НПО Мир и семья ; Санкт Петербург, 2003 г.) …   Словарь металлургических терминов

• rolling — index fluvial Burton s Legal Thesaurus. William C. Burton. 2006 …   Law dictionary

• rolling — rollingly, adv. /roh ling/, n. 1. the action, motion, or sound of anything that rolls. adj. 2. moving by revolving or turning over and over. 3. rising and falling in gentle slopes, as land. 4. moving in undulating billows, as clouds or waves. 5.… …   Universalium

• Rolling — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Sommaire 1 Patronyme 2 Pseudonyme 3 Musiqu …   Wikipédia en Français