A sphere of relative density $\sigma$ and diameter $D$ has concentric cavity of diameter $d$. The ratio of $\frac{D}{d}$, if it just floats on water in a tank is:
$\left(\frac{\sigma}{\sigma-1}\right)^{\frac{1}{3}}$
$\left(\frac{\sigma+1}{\sigma-1}\right)^{\frac{1}{3}}$
$\left(\frac{\sigma-1}{\sigma}\right)^{\frac{1}{3}}$
$\left(\frac{\sigma-2}{\sigma+2}\right)^{\frac{1}{3}}$
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 vessel contains oil (density =$ 0.8 \;gm/cm^3$) over mercury (density = $13.6\; gm/cm^3$). A homogeneous sphere floats with half of its volume immersed in mercury and the other half in oil. The density of the material of the sphere in $ gm/cm^3$ is
A sphere of solid material of relative density $9$ has a concentric spherical cavity and floats having just sinked in water. If the radius of the sphere be $R$, then the radius of the cavity $(r)$ will be related to $R$ as :-
The reading of spring balance when a block is suspended from it in air, is $60\,N$. This reading is changed to $40\, N$ when the block is immersed in water. The specific density of the block is
A candle of diameter $ d$ is floating on a liquid in a cylindrical container of diameter $D $ $(D>>d)$ as shown in figure. If it is burning at the rate of $2$ cm/hour then the top of the candle will