General Knowledge- Physics (Floatation)

Floatation

            Buoyant Force: When a body is immersed partly or wholly in a liquid, a force acts on the body by t he liquid in upward direction. This force is call Buoyant force or force of buoyancy or up thrust. It is equal to the weight of the liquid displaced by the body and acts at the center of gravity of displaced liquid. Its study was first made by Archimedes.

            Archimedes Principle: When a body immersed in a liquid partly or wholly in a liquid, there is an apparent loss in the weight of the body which equal to weight of the liquid displaced by the body.

Law of Floatation

            A body floats in liquid if

(i)                 Density of material of body is less than or equal to the density of liquid.

(ii)               If density of material of body is equal to density of liquid, the body floats fully submerged in liquid in neutral equilibrium.

(iii)             When body floats in neutral equilibrium the weight of the body is equal to the weight of displaced liquid.

(iv)             The central of gravity of body and central of gravity of displaced liquid should be in same vertical line.

            Center of Buoyancy: The center of gravity of the liquid displaced by a body is called center of buoyancy.

            Meta Center: When a floating body is slightly tilted from equilibrium position, the center of buoyancy shifts. The point where the vertical line passing through the new position of center of buoyancy meets with the initial line is called Meta center.

Condition for stable equilibrium for a Floating body:

(i)                 The meta center must be always greater than the center of gravity of the body.

(ii)               The line joining center of gravity of the body and center of flotation should be vertical

Density: Density is defined as the mass per unit volume.

                  Density = Mass/Volume, its SI unit is kg/m³

                  Relative density = density of material / density of water at 4^o C

Since, relative density is a ratio so it is unit less.

►Relative density is measured by Hydrometer.

►The density of sea water is more than that of normal water. This explains why it is easier to swim in sea water.

► When ice floats in water its 1/10 the part remains outside the water.

►If ice floating in water in a vessel melts; the level of water in water does not change.

►Purity of milk is measured by lactometer.

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