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GCSE Bitesize was launched in January 1998, covering seven subjects. For each subject, a one- or two-hour long TV programme would be broadcast overnight in the BBC Learning Zone block, and supporting material was available in books and on the BBC website. At the time, only around 9% of UK households had access to the internet at home.
Roller bearings are the earliest known type of rolling-element-bearing, dating back to at least 40 BC. Common roller bearings use cylinders of slightly greater length than diameter. Roller bearings typically have a higher radial load capacity than ball bearings, but a lower capacity and higher friction under axial loads.
A ball bearing. A bearing is a machine element that constrains relative motion to only the desired motion and reduces friction between moving parts.The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts.
Tapered roller bearings were a breakthrough at the end of the 19th century because bearings used in wheel axles had not changed much since ancient times. They consisted of a cylindrical seat on the frame and part of the axle enclosed in a case or box that held a lubricant.
In the case of ball bearings, the bearing has inner and outer races and a set of balls. Each race is a ring with a groove where the balls rest. The groove is usually shaped so the ball is a slightly loose fit in the groove. Thus, in principle, the ball contacts each race at a single point.
Bearing(s) may refer to: Bearing (angle), a term for direction; Bearing (mechanical), a component that separates moving parts and takes a load;
A linear-motion bearing or linear slide is a bearing designed to provide free motion in one direction. There are many different types of linear motion bearings. Motorized linear slides such as machine slides, X-Y tables , roller tables and some dovetail slides are bearings moved by drive mechanisms.
BBC Online, formerly known as BBCi, is the BBC's online service. It is a large network of websites including such high-profile sites as BBC News and Sport, the on-demand video and radio services branded BBC iPlayer and BBC Sounds, the children's sites CBBC and CBeebies, and learning services such as Bitesize and Own It.