A solid sphere of radius $R$ and density $\rho$ is attached to one end of a mass-less spring of force constant $k$. The other end of the spring is connected to another solid sphere of radius $R$ and density $3 p$. The complete arrangement is placed in a liquid of density $2 p$ and is allowed to reach equilibrium. The correct statement$(s)$ is (are)

$(A)$ the net elongation of the spring is $\frac{4 \pi R^3 \rho g}{3 k}$

$(B)$ the net elongation of the spring is $\frac{8 \pi R^3 \rho g}{3 k}$

$(C)$ the light sphere is partially submerged.

$(D)$ the light sphere is completely submerged.

A rectangular box has water in it. It is being pulled to the right with an acceleration $a$. Which of the following options shows the correct shape of water surface on it ?

A block of wood floats in water with $\frac{4}{5}$ th of its volume submerged, but it just floats in another liquid. The density of liquid is (in $kg / m ^3$ )

A hollow sphere has inner volume half the outer volume. Its $4/5\,th$ part is submerged when placed in water. The density of material is

A boat having a length of $3\,metre$ and breadth $2\,metre$ is floating on a lake. The boat sinks by one cm when a man gets on it. Mass of the man is ....... $kg$

Write the only equation for the volume of partially immerged part of body float on the surface of liquid.