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Balance of forces on objects with negative, neutral and positive buoyancy A neutrally buoyant diver does not need to fin to maintain depth. In scuba diving, the ability to maintain neutral buoyancy through controlled breathing, accurate weighting, and management of the buoyancy compensator is an important skill. A scuba diver maintains neutral ...
Thus, the net force on the object is the difference between the magnitudes of the buoyant force and its weight. If this net force is positive, the object rises; if negative, the object sinks; and if zero, the object is neutrally buoyant—that is, it remains in place without either rising or sinking.
Buoyancy is a function of the force of gravity or other source of acceleration on objects of different densities, and for that reason is considered an apparent force, in the same way that centrifugal force is an apparent force as a function of inertia. Buoyancy can exist without gravity in the presence of an inertial reference frame, but ...
The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect can be useful to drive natural ventilation in certain climates, but in other circumstances may be a cause of unwanted air infiltration or fire ...
During the dive, buoyancy is controlled by adjusting the volume of air in the buoyancy compensation device (BCD) and, if worn, the dry suit, in order to achieve negative, neutral, or positive buoyancy as needed. The amount of weight required is determined by the maximum overall positive buoyancy of the fully equipped but unweighted diver ...
Competent recreational scuba divers will usually spend most of a dive at near neutral buoyancy and level trim, clear of the bottom and other solid surfaces. When working on the bottom it is usually safer and more comfortable to be trimmed more upright, particularly in a dry suit, and negative buoyancy can help stability while working.
Negative buoyancy: to descend or settle on the bottom. Neutral buoyancy: when the diver wants to remain at a constant depth. Positive buoyancy: when the diver wants to float on the surface. A small amount of positive buoyancy my be used to ascend, but the diver must monitor it constantly and vigilantly to keep from ascending too quickly.
These effects are mostly consequences of immersion in water, the hydrostatic pressure of depth and the effects of pressure and temperature on breathing gases. An understanding of the physics behind is useful when considering the physiological effects of diving, breathing gas planning and management, diver buoyancy control and trim , and the ...