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Buoyancy (/ ˈ b ɔɪ ən s i, ˈ b uː j ən s i /), [1] [2] or upthrust is a net upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid.
In other words, for an object floating on a liquid surface (like a boat) or floating submerged in a fluid (like a submarine in water or dirigible in air) the weight of the displaced liquid equals the weight of the object. Thus, only in the special case of floating does the buoyant force acting on an object equal the objects weight.
A pontoon boat is a flattish boat that relies on nautical floats for buoyancy. Common boat designs are a catamaran with two pontoons, or a trimaran with three. [2] In many parts of the world, pontoon boats are used as small vehicle ferries to cross rivers and lakes. [3] An anchored raft-like platform used for diving, often referred to as a pontoon
In a flying boat, the main source of buoyancy is the fuselage, which acts like a ship's hull in the water because the fuselage's underside has been hydrodynamically shaped to allow water to flow around it. Most flying boats have small floats mounted on their wings to keep them stable.
Rivers present special hazards to vessels. They usually have varying water flows that alternately lead to high speed water flows or protruding rock hazards. Changing siltation patterns may cause the sudden appearance of shoal waters, and often floating or sunken logs and trees (called snags) can endanger the hulls and propulsion of riverboats.
In his research, Archimedes discovered that an object is buoyed up by a force equal to the weight of the water displaced by the object. In other words, an inflatable boat that displaces 100 pounds (45 kilograms) of water is supported by the same amount of force. An object that floats in a fluid is known as being positively buoyant.
Short S23 "C" Class or "Empire" flying boat A PBM Mariner takes off in 1942 Dornier X in 1932. A flying boat is a type of seaplane with a hull, allowing it to land on water. [1] It differs from a floatplane in having a fuselage that is purpose-designed for flotation, while floatplanes rely on fuselage-mounted floats for buoyancy.
A boat differs from a raft by obtaining its buoyancy by having most of its structure exclude water with a waterproof layer, e.g. the planks of a wooden hull, the hide covering (or tarred canvas) of a currach. In contrast, a raft is buoyant because it joins components that are themselves buoyant, for example, logs, bamboo poles, bundles of reeds ...