$A$ cubical block of side $0.5\,m$ floats on water with $30\%$ of its volume under water. What is the maximum weight (in $kg$) that can be put on the block without fully submerging it under water? [Take density of water $= 10^3\,kg/m^3$]

An empty glass jar is submerged in a tank of water with the open mouth of the jar downwards, so that the air inside the jar is trapped and cannot escape. As the jar is pushed down slowly, the magnitude of the net buoyant force on the system of the volume of gas trapped in the jar and the jar:

$A$ solid sphere of specific gravity $27$ has a concentric spherical cavity and it just sinks in water. The ratio of the cavity radius to the outer radius of the sphere is

$A$ soft plastic bottle,filled with water of density $1 \text{ g/cc}$,contains an inverted glass test-tube with some air (ideal gas) trapped inside,as shown in the figure. The test-tube has a mass of $5 \text{ g}$,and it is made of thick glass with a density of $2.5 \text{ g/cc}$. Initially,the bottle is sealed at atmospheric pressure $P_0 = 10^5 \text{ Pa}$,such that the volume of the trapped air is $V_0 = 3.3 \text{ cc}$. When the bottle is squeezed from the outside at a constant temperature,the pressure inside increases and the volume of the trapped air decreases. It is observed that the test-tube begins to sink at a pressure $P_0 + \Delta P$ without changing its orientation. At this pressure,the volume of the trapped air is $V_0 - \Delta V$.
Let $\Delta V = X \text{ cc}$ and $\Delta P = Y \times 10^3 \text{ Pa}$.
$(1)$ The value of $X$ is
$(2)$ The value of $Y$ is

$A$ dumbbell is placed in water of density $\rho$. It is observed that by attaching a mass $m$ to the rod,the dumbbell floats with the rod horizontal on the surface of water and each sphere exactly half submerged as shown in the figure. The volume of the mass $m$ is negligible. The value of length $l$ is

$A$ body of density $1.2 \times 10^{3} \text{ kg/m}^3$ is dropped from rest from a height $1 \text{ m}$ into a liquid of density $2.4 \times 10^{3} \text{ kg/m}^3$. Neglecting all dissipative effects, the maximum depth to which the body sinks before returning to float on the surface is: (in $\text{ m}$)