A $0.5\ kg$ mass of lead is submerged in a container filled to the brim with water and a block of wood floats on top. The lead mass is slowly lifted from the container by a thin wire and as it emerges into air the level of the water in the container drops a bit. The lead mass is now placed on the block of wood. As the lead is placed on the wood.

Four identical beakers contain same amount of water as shown below. Beaker $A$ contains only water. A lead ball is held submerged in the beaker $B$ by string from above. A same sized plastic ball, say a table tennis $(TT)$ ball, is held submerged in beaker $C$ by a string attached to a stand from outside. Beaker $D$ contains same sized $TT$ ball which is held submerged from a string attached to the bottom of the beaker. These beakers (without stand) are placed on weighing pans and register readings $w_{A}, w_{B}, w_{C}$ and $w_{D}$ for $A, B, C$ and $D$, respectively. Effects of the mass and volume of the stand and string are to be neglected.

The density of ice is $0.9 \,g / cm ^3$. What percentage by volume of the block of ice floats outside the water is ……….$\%$

A metal ball of density $7800\  kg/m^3$ is suspected to have a large number of cavities . It weighs $9.8$ $kg$ when weighed directly on a balance and $1.5$ $kg$ less when immersed in water . The fraction by volume of the cavities in the metal ball is approximately ……. $\%$

A sample of metal weighs $210 gm$  in air, $180 gm$  in water and $120 gm$  in liquid. Then relative density $(RD) $ of