Work of $3.0\times10^{-4}$ joule is required to be done in increasing the size of a soap film from $10\, cm\times6\, cm$ to $10\, cm\times11\, cm$. The surface tension of the film is

A spherical body of mass $m$ and radius $r$ is allowed to fall in a medium of viscosity $\eta $. The time in which the velocity of the body increases from zero to $0.63\, times$ the terminal velocity $(v)$ is called time constant $\left( \tau  \right)$. Dimensionally $\tau $ can be represented by

The work done in splitting a drop of water of $1\, mm$ radius into $10^6$ droplets is (surface tension of water $72\times10^{-3}\, N/m$) :

Horizontal tube of non-uniform cross-section has radius of $0.2\,m$ and $0.1\,m$ respectively at $P$ and $Q$. For streamline flow of liquid, the rate of liquid flow

Water rises to a height of $10\, cm$ in capillary tube and mercury falls to a depth of $3.1\,cm$ in the same capillary tube. If the density of mercury is $13.6$ and the angle of contact for mercury is $135^o$, the approximate ratio of surface tensions of water and mercury is

A boat carrying a number of stones is floating in a water tank. If the stones are unloaded into water, the water level in the tank will ............