PRESSURE
When a body is thrown into a liquid,one of the following may happen
When a body of density and volume V is immersed in a liquid of density ,the force is acting on the body are:
(1) Weight of the body W = mg = \(V{\rho _b}g\) acting vertically downwards through the centre of gravity of the body.
(2) the upthrust \(B=V{\rho _b}g\) acting vertically upwards through the centre of gravity of the displaced liquid which is also known as the centre of buoyancy.
So, the following then situations are possible when the body is released.
a)(\({\rho _b} > {\rho _L}\))
1.The body may sink in the liquid:It happens,when the weight of the liquid displaced (upthrust of the liquid)is less than the weight of the body .In case,the body is not hollow from inside,then density of the material of the body must be greater than the density of the liquid
In this situation, 'W' is more than 'B' and hence the body will sink normal to the free surface
b) \(\rho_B=\rho_L\)
2.The body may float just completely submerged in the liquid:It happens,when when the weight of the liquid displaced is just equal to the weight of the body .Again if the body is not hollow from inside,then density of the material of the body must be equal to the density of the liquidc) .
In this situation, W = B so, the body will float while it is fully submerged or just floats in liquid or just immersed in liquid.
3.\(\rho_B<\rho_L\)
3.The body may float with a part submerged in the liquid:It happens ,when the weight of the of the liquid displaced by the submerged part in the liquid is equal to the weight of the body .Again if the body is not hollow from inside,then density of the material of the body must be less than the density of the liquid
In this situation, W<B. So, the body will move upwards normal to free surface. After some oscillation, it will finally settle in an equilibrium position while partially submerged.