$A$ pin or a needle floats on the surface of water,the reason for this is:

Air (density $\rho$) is being blown on a soap film (surface tension $T$) by a pipe of radius $R$ with its opening right next to the film. The film is deformed and a bubble detaches from the film when the shape of the deformed surface is a hemisphere. Given that the dynamic pressure on the film due to the air blown at speed $v$ is $\frac{1}{2} \rho v^{2}$,the speed at which the bubble is formed is:

$A$ steel coin of thickness $d$ and density $\rho$ is floating on water of surface tension $T$. The radius of the coin $R$ is [ $g$ = acceleration due to gravity]

It is better to wash clothes in hot water than in cold water. Explain.

$A$ drop of some liquid of volume $0.04 \ cm^{3}$ is placed on the surface of a glass slide. Then another glass slide is placed on it in such a way that the liquid forms a thin layer of area $20 \ cm^{2}$ between the surfaces of the two slides. To separate the slides a force of $16 \times 10^{5} \ dyne$ has to be applied normal to the surfaces. The surface tension of the liquid is (in $dyne \ cm^{-1}$):

$A$ soap film is formed on a circular frame. $A$ loop of thread is lying on the film. If the film inside the loop is broken,then the tension in the thread will be: ($R =$ radius of the loop,$T =$ surface tension of the liquid)