Stable Equilibrium of Submerged Bodies
The equilibrium state of a submerged body depends on the relative positions of its centre of gravity (G) and its centre of buoyancy (B).
The centre of buoyancy (B) is the point where the upward buoyant force acts, which is the centroid of the volume of fluid displaced by the body.
The centre of gravity (G) is the point where the entire weight of the body acts vertically downwards.
Condition for Stable Equilibrium
For a submerged body to be in stable equilibrium, it must return to its original orientation when slightly disturbed. This occurs when:
- The centre of gravity (G) is located below the centre of buoyancy (B).
If G is below B, any slight tilt creates a restoring moment due to the weight and buoyant force acting along different vertical lines, bringing the body back to its stable position.
Other Equilibrium Conditions
- Unstable Equilibrium: Occurs when G is above B. Any tilt creates a moment that increases the tilt.
- Neutral Equilibrium: Occurs when G coincides with B. Any tilt does not change the relative position, and the body remains in its new orientation.
Therefore, for a submerged body to be in stable equilibrium, the centre of gravity must be positioned below the centre of buoyancy.
Important Questions from Buoyancy and Floatation
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