BUOYANCY AND FLOATATION: 1

 BUOYANCY

    When a body is immersed in a fluid, an upward force is exerted by the fluid on the body. This upward force is equal to the weight of the fluid displaced by the body and is called the force of buoyancy or simply buoyancy.

CENTRE OF BUOYANCY

    It is defined as the point, through which the force of buoyancy is supposed to act. As the force of buoyancy is a vertical force and is equal to the weight of the fluid displaced by the body, the centre of buoyancy will be the centre of  gravity of the fluid displaced.

META CENTRE

    It is defined as the point about which a body starts oscillating when the body is tilted by a small angle. The meta centre may also be defined as the point at which the line of action of force of buoyancy will meet the normal axis of the body when the body is given a small angular displacement. 

    consider a body floating in a liquid as shown in fig. a Let the body is in equilibrium and G is the centre of gravity and B the centre of buoyancy. For equilibrium, both the point lie on the normal axis, which is vertical.

FIG. BUOYANCY AND FLOATATION

    Let the body is given a small angular displacement in the clockwise direction as shown in fig. b the centre of buoyancy, which is the centre of gravity of the displaced liquid or the centre of gravity of the portion of the body sub-merged in liquid, will now be shifted towards right from the normal axis. Let it is at B1 as shown in fig. b The line of action of the force of buoyancy in this new position, will intersect the normal axis of the body at same point say M. This point M is called meta centre.

META CENTRIC HEIGHT

    The distance MG in fig. b i.e., the distance between the meta centre of a floating body and the centre of gravity of the body is called meta centric height.

Also read Bernoulli's principle

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