What is buoyancy?

$A$ cubical block of wood of edge $10$ $cm$ and mass $0.92$ $kg$ floats in a tank of water with a layer of oil of relative density $0.6$ to a depth of $4$ $cm$ above the water. When the block attains equilibrium with four of its side edges vertical,which of the following is true?

$A$ silver ingot weighing $2.1 \ kg$ is held by a string so as to be completely immersed in a liquid of relative density $0.8$. The relative density of silver is $10.5$. The tension in the string in $kg-wt$ is

An object of mass $10 \ kg$ is released from rest in a liquid. If the object moves a distance of $2 \ m$ while sinking in a time duration of $1 \ s$,then the mass of the liquid displaced by the submerged object is $(g = 10 \ m/s^2)$. (in $kg$)

$A$ piece of metal weighs $45 \ g$ in air and $25 \ g$ in a liquid of density $1.5 \times 10^3 \ kg \ m^{-3}$ kept at $30^{\circ} C$. When the temperature of the liquid is raised to $40^{\circ} C$,the metal piece weighs $27 \ g$. The density of the liquid at $40^{\circ} C$ is $1.25 \times 10^3 \ kg \ m^{-3}$. The coefficient of linear expansion of the metal is:

$A$ sphere of diameter $7 \, cm$ and mass $266.5 \, g$ floats in a bath of a liquid. As the temperature is raised,the sphere just begins to sink at a temperature $35^{\circ} C$. If the density of the liquid at $0^{\circ} C$ is $1.527 \, g/cm^3$,then neglecting the expansion of the sphere,the coefficient of cubical expansion of the liquid is: