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screw

(Encyclopedia)screw, simple machine consisting essentially of a solid cylinder, usually of metal, around which an inclined plane winds spirally, either clockwise or counterclockwise. It is used to fasten one object...

ion, in chemistry

(Encyclopedia)ion, atom or group of atoms having a net electric charge. Ionization has many applications. Vapor lamps and fluorescent lamps take advantage of the light given off when positive ions recombine with ...

Monitor and Merrimack

(Encyclopedia)Monitor and Merrimack, two American warships that fought the first engagement between ironclad ships. When, at the beginning of the Civil War, the Union forces abandoned the Norfolk Navy Yard at Ports...

flight

(Encyclopedia)CE5 Aircraft motions and control surfaces: Yaw, or motion to the left or right, is controlled by the rudder. Pitch, or climbing or dropping, is controlled by the elevators, which move in the same d...

glider

(Encyclopedia)glider, type of aircraft resembling an airplane but having at most a small auxiliary propulsion plant and usually no means of propulsion at all. The typical modern glider has very slender wings and a ...

pulley

(Encyclopedia)CE5 Pulleys: The mechanical advantage (MA) of a system of pulleys is equal to the number of supporting strands: in A MA=1 and in B MA=2. pulley, simple machine consisting of a wheel over which a r...

Riga

(Encyclopedia)Riga rēˈgə [key], city (2011 provisional pop. 657,424), capital of Latvia, on the Daugava (Western Dvina) River near its entry into the Gulf of Riga. A major Baltic port, it is also a rail junction...

Industrial Revolution

(Encyclopedia)Industrial Revolution, term usually applied to the social and economic changes that mark the transition from a stable agricultural and commercial society to a modern industrial society relying on comp...

Brown, John, American abolitionist

(Encyclopedia)Brown, John, 1800–1859, American abolitionist, b. Torrington, Conn. He spent his boyhood in Ohio. Before he became prominent in the 1850s, his life ha...

transportation

(Encyclopedia)transportation, conveyance of goods and people over land, across water, and through the air. See also commerce. The first practical attempts at air transportation began with the invention of the h...