 Welcome back MechanicalEI. Did you know that invention of bearings in the form of wooden rollers may predate the invention of wheels? This makes us wonder, what are bearings? Before we jump in, check out the previous part of the series to learn about what couplings are. Now, 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 linear movement of the moving part or free rotation around a fixed axis. Or, it may prevent motion by controlling the vectors of normal forces that bear on the moving parts. A slide bearing is the simplest type of bearing, comprising of just a bearing surface and no rolling elements. Wherein, a journal which is the part of the shaft in contact with the bearing slides over the bearing surface. The simplest example of a slide bearing is a shaft rotating in a hole. Plain bearings in general are the least expensive type of bearings. They are also compact and lightweight and they have a high load carrying capacity. A rolling element bearing is a bearing which carries the load by placing balls or rollers between two bearing rings called races. The relative motion of races causes rolling elements to roll with minimal rolling resistance and with little sliding. They require fewer boundary dimensions and can transmit heavy and variable loads of various forms. They can easily be installed, serviced and replaced. Fluid bearings are bearings in which the load is solely supported by a thin layer of rapidly moving pressurized liquid or gas between the bearing surfaces. Since there is no contact between the moving parts, there is no sliding friction. Allowing fluid bearings to have lower friction, fear and vibration than many other types of bearings. When compared, a fluid bearing can be as simple as two smooth surfaces with seals to keep in the working fluid. In contrast, a conventional rolling element bearing may require many high precision rollers with complicated shapes. Hence, we first saw what bearings are, then saw what simple type of bearing is and finally went on to see what rolling element and fluid types of bearings are. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also, thanks a lot for those constructive comments. You helped the channel grow. So, here are the top mechanical EIs of our last videos. In the next episode of Mechanical EI, find out what conventions in bearings are.