A square frame of each side ' $L$ ' is dipped in a soap solution and taken out. The force acting on the film…
A square frame of each side ' $L$ ' is dipped in a soap solution and taken out. The force acting on the film formed is $(\mathrm{T}=$ surface tension of soap solution)
8TL
2TL
4TL
$6 \mathrm{TL}$
Solution
Soap film has two surfaces.
Net force acting on frame $=2$ (force on one surface)
$\begin{aligned} & =2 \times \mathrm{T} \times \text { (perimeter) } \\ & =2 \times \mathrm{T} \times 4 \mathrm{~L}\end{aligned}$
Net force acting on the square frame $=8 \mathrm{TL}$