stability(redirected from stabilities)
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state of balance. When a body or a system is in equilibrium, there is no net tendency to change. In mechanics, equilibrium has to do with the forces acting on a body.
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of a vessel, the ability of a vessel to withstand the external forces that cause it to roll or pitch and to return to the original equilibrium position after these forces have ceased to operate. Stability is one of the most important seakeeping qualities of a vessel. Resistance to rolling is called transverse stability, and resistance to pitching is called longitudinal stability. Because of the elongated shape of a vessel, its longitudinal stability is significantly greater than its transverse stability. Hence assurance of proper transverse stability for safety at sea is a more important design consideration.
A distinction is made between static stability and dynamic stability. Static stability is measured in terms of the righting moment that is developed when a vessel is tilted to a certain angle of heel or trim, and the dynamic stability is measured in terms of the work of this moment. For small angles of heel the righting moment is approximately proportional to the angle of heel, the displacement, and the metacentric height.
Under operating conditions, the transverse stability is checked by determining the metacentric height and comparing it with the value that is safe for the particular vessel. Standards for transverse stability are set by the classification societies.
L. N. STRELIAEV
ii. A state of atmosphere in which the vertical distribution of temperature is such that a parcel of air will resist displacement from its initial level.