$A$ piece of copper having an internal cavity weighs $264\, g$ in air and $221\, g$ in water. Find the volume (in $cc$) of the cavity. Density of $Cu = 8.8\, g/cc$.

$A$ wooden cube of side $10 \ cm$ floats at the interface between water and oil with its lower surface $3 \ cm$ below the interface. If the density of oil is $0.9 \ g \ cm^{-3}$, the mass of the wooden cube is (in $g$)

$A$ balloon of mass $m$ contains water of mass $M$. If it is completely immersed in water, find the apparent mass of the balloon with water in it.

$A$ wooden cube floats in water when a $200\,g$ mass is placed on it. When the mass is removed,the cube rises by $2\,cm$ above the water level. The side of the cube is ......... $cm$.

$A$ small wooden ball of density $\rho$ is immersed in water of density $\sigma$ to a depth $h$ and then released. The height $H$ above the surface of water up to which the ball will jump out of water is

$A$ boy has a mass of $60\, kg$. He wants to swim in a river with the help of a wooden log. If the relative density of the wood is $0.6$,what is the minimum volume of the wooden log required? (Density of river water is $1000\, kg/m^3$)