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Door Stop
A doorstop (also door stopper, door stop or door wedge) is an object or device used to hold a door open or closed, or to prevent a door from opening too widely. The same word is used to refer to a thin slat built inside a door frame to prevent a door from swinging through when closed. A doorstop (applied) may also be a small bracket or 90-degree piece of metal applied to the frame of a door to stop the door from swinging (bi-directional) and converting that door to a single direction (in-swing push or out-swing pull). The doorstop can be a separate part or integrated with a hinge or door closer. Also called a tanogen. History Formally-produced doorstops trace their history to the 18th century in Europe, becoming widely manufactured in Europe in the early 19th century. By the mid 19th century, manufacturing had primarily moved to the United States. Despite their early manufacturing, credit for the invention of the doorstop is usually granted to Osburn Dorsey, an African American ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wooden Wedge Door Stop
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or woodchips or fiber. Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons, furniture and paper. More recently it emerged as a feedstock for the production ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Door
A door is a hinged or otherwise movable barrier that allows ingress (entry) into and egress (exit) from an enclosure. The created opening in the wall is a ''doorway'' or ''portal''. A door's essential and primary purpose is to provide security by controlling access to the doorway (portal). Conventionally, it is a panel that fits into the doorway of a building, room, or vehicle. Doors are generally made of a material suited to the door's task. They are commonly attached by hinges, but can move by other means, such as slides or counterbalancing. The door may be able to move in various ways (at angles away from the doorway/portal, by sliding on a plane parallel to the frame, by folding in angles on a parallel plane, or by spinning along an axis at the center of the frame) to allow or prevent ingress or egress. In most cases, a door's interior matches its exterior side. But in other cases (e.g., a vehicle door) the two sides are radically different. Many doors incorporate locking ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
African Americans
African Americans (also referred to as Black Americans and Afro-Americans) are an ethnic group consisting of Americans with partial or total ancestry from sub-Saharan Africa. The term "African American" generally denotes descendants of enslaved Africans who are from the United States. While some Black immigrants or their children may also come to identify as African-American, the majority of first generation immigrants do not, preferring to identify with their nation of origin. African Americans constitute the second largest racial group in the U.S. after White Americans, as well as the third largest ethnic group after Hispanic and Latino Americans. Most African Americans are descendants of enslaved people within the boundaries of the present United States. On average, African Americans are of West/ Central African with some European descent; some also have Native American and other ancestry. According to U.S. Census Bureau data, African immigrants generally do not se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wedge (mechanics)
A wedge is a triangular shaped tool, and is a portable inclined plane, and one of the six simple machines. It can be used to separate two objects or portions of an object, lift up an object, or hold an object in place. It functions by converting a force applied to its blunt end into forces perpendicular (normal) to its inclined surfaces. The mechanical advantage of a wedge is given by the ratio of the length of its slope to its width..''McGraw-Hill Concise Encyclopedia of Science & Technology'', Third Ed., Sybil P. Parker, ed., McGraw-Hill, Inc., 1992, p. 2041. Although a short wedge with a wide angle may do a job faster, it requires more force than a long wedge with a narrow angle. The force is applied on a flat, broad surface. This energy is transported to the pointy, sharp end of the wedge, hence the force is transported. The wedge simply transports energy in the form of friction and collects it to the pointy end, consequently breaking the item. History Wedges have exi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into ''static friction'' ("stiction") between non-moving surfaces, and ''kinetic friction'' between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1). *Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. *Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. *Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. *Internal friction is the force resisting motion between the elements making up a sol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
