outside surface friction
81coal mining — Coal was very important in the economic development of Britain. It was used as fuel in the factories built during the Industrial Revolution and continued to be important until the 1980s. The main coalfields are in north east England, the north… …
82Formation and evolution of the Solar System — Artist s conception of a protoplanetary disk The formation and evolution of the Solar System is estimated to have begun 4.568 billion years ago with the gravitational collapse of a small part of a giant molecular cloud …
83airplane — /air playn /, n. 1. a heavier than air aircraft kept aloft by the upward thrust exerted by the passing air on its fixed wings and driven by propellers, jet propulsion, etc. 2. any similar heavier than air aircraft, as a glider or helicopter. Also …
84Saturn — /sat euhrn/, n. 1. an ancient Roman god of agriculture, the consort of Ops, believed to have ruled the earth during an age of happiness and virtue, identified with the Greek god Cronus. 2. Astron. the planet sixth in order from the sun, having an …
85Western architecture — Introduction history of Western architecture from prehistoric Mediterranean cultures to the present. The history of Western architecture is marked by a series of new solutions to structural problems. During the period from the… …
86Rotating locomotion in living systems — A passive wheel Rotating locomotion encompasses two distinct modes of …
87Nanotube nanomotor — A device generating linear or rotational motion using carbon nanotube(s) as the primary component, is termed a nanotube nanomotor. Nature already has some of the most efficient and powerful kinds of nanomotors. Some of these natural biological… …
88Metalworking — Machining a bar of metal on a lathe. Metalworking is the process of working with metals to create individual parts, assemblies, or large scale structures. The term covers a wide range of work from large ships and bridges to precise engine parts… …
89List of Chinese inventions — A bronze Chinese crossbow mechanism with a buttplate (the wooden components have …
90hand tool — any tool or implement designed for manual operation. * * * Introduction any of the implements used by craftsmen in manual operations, such as chopping, chiseling, sawing, filing, or forging. Complementary tools, often needed as auxiliaries to… …
