Write the law of floatation and describe its cases.
Write the law of floatation and describe its cases.
"When the weight of a body is equal to the weight of liquid displaced by the part of the body immerged in it, the body floats on the surface of the liquid."
For example : Boat, Steamer.
When a body is partially or completely immerged in a liquid, it experiences two forces.
$(1)$ Weight of the body $\mathrm{W}=m g$
$=\rho_{f} V_{s} g($ in downward $)$
Where $m=$ volume $\times$ density $\left(\mathrm{V}_{s} \rho_{s}\right)$ and $\mathrm{V}_{s}=$ volume of body, $\rho_{s}=$ density of body.
$(2)$ Buoyant force of body,
$\mathrm{F}_{b}=$ weight of displaced liquid
$=\rho_{f} V_{s} g$ (in upward direction)
where $V_{f}=$ volume of displaced liquid,
$\rho_{f}=$ Density of liquid
Cases:
$(a)$ If $\mathrm{W}>\mathrm{F}_{b}$, the body sinks.
Example : Piece of iron
$(b)$ If $\mathrm{W}=\mathrm{F}_{b}$, the body remains in equilibrium at any depth.
Example : Submarine.
$(c)$ If $\mathrm{W}<\mathrm{F}_{b}$ the body floats on the surface of the liquid.
For example : Submarine, boat
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