Soap solution is used for cleaning dirty clothes because

$A$ paper disc of radius $R$ from which a circular hole of radius $r$ is cut out,is floating in a liquid of surface tension $T$. The force on the disc due to surface tension will be

$A$ square frame of each side $L$ is dipped in a soap solution and taken out. The force acting on the film formed is ($T =$ surface tension of soap solution). (in $TL$)

$A$ thin metal disc of radius $r$ floats on water surface and bends the surface downwards along the perimeter,making an angle $\theta$ with the vertical edge of the disc. If the weight of water displaced by the disc is $W$,the weight of the metal disc is [$T =$ surface tension of water].

Why does the free surface of a liquid tend to contract?

$A$ square frame of side $L$ is dipped in a liquid. On taking out,a membrane is formed. If the surface tension of the liquid is $T$,the force acting on the frame will be (in $TL$)