What is neutral buoyancy?
Buoyancy is the net upward force experienced by an object in a fluid. Pascal's principle dictates that fluid pressure on an object increases with depth, so there is greater pressure on the bottom of the object than the top, resulting in a net upward force. When an object's buoyancy is greater than its weight, the object will float.
An object with neutral buoyancy has a density such that when it is fully submerged the upward force due to buoyancy is exactly equal to the downward force due to the weight of the object.
In pure water this is a density of 1000 kg/m3 (1kg/litre)
In sea water this is a density of about 1025 kg/m3 (1.025kg/litre)
Consider a submarine. A sub with negative buoyancy would tend to sink . Positive buoyancy would cause it to sink. A sub with neutral buoyancy would remain at a steady depth.
Positive buoyancy . . . When the object is completely submerged, the net force on it ... the combination of gravity down and buoyancy up ... is upward, so the object tries to rise. Negative buoyancy . . . When the object is completely submerged, the net force on it ... the combination of gravity down and buoyancy up ... is downward, so the object tries to sink. Neutral buoyancy . . . When the…
If the water displaced by the object in it weighs more than the object itself, the object will have positive buoyancy and float. If the displaced water weighs less than the object in it, the object becomes negatively buoyant and will sink. If the displaced water and the object weigh the same, neutral buoyancy will be achieved, and no change in depth will occur.