A water jet of radius $R$ is shown in the figure. The force between the part $1$ and part $2$ at the section $ABCD$ due to the surface tension is : (Assume that, $T$ is surface tension)

 

A wire is bend at an angle $\theta$. A rod of mass $m$ can slide along the bended wire without friction as shown in figure. If a soap film is maintained in the frame and frame is kept in a vertical position and rod is in equilibrium. If rod is displaced slightly in vertical direction. The time period of small oscillation is $a\pi \sqrt{\frac{bl}{g}}$ sec. where $a$ and $b$ are constant number then $a+b$ is

Consider a $\mathrm{U}$-shaped frame with a sliding wire of length $l$ and mass $m$ on its arm. It is dipped in a soap solution that taken out and placed in vertical position as shown in the figure. Choose a minimum value of $m$, so that the wire does not descend (surface tension of soap solution is $S$):

An oil drop falls through the air with a terminal velocity of $5 \times {10}^{–4} \mathrm{m} {\mathrm{s}}^{-1}$. The radius of the drop will be: $\eta =3.6\times {10}^{-5 }\mathrm{N} \mathrm{s} {\mathrm{m}}^{-2}, {\mathrm{\rho }}_{\mathrm{oil}}=900 \mathrm{kg} {\mathrm{m}}^{-3}$.,$g=10 \mathrm{m} {\mathrm{s}}^{-2}$

Neglect the density of air as compared to oil.