BUOYANCY

  Buoyancy principle:
      It is force produced due to fluid pressure.       
        

When a body is immersed in a liquid, it is lifted up by a force equal to weight of liquid displaced by the body. The tendency of liquid to lift up an immersed body is buoyancy. The upward thrust of liquid to lift up the body is called buoyancy force.
                           (or)

        When an object is fully or partially immersed in a fluid, due to the pressure difference of the fluid between the top and bottom of the object, buoyant force acts on the object causing it to float.

The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body.

Buoyancy is important for boats, ships , balloons and airships.