Question

A thread is tied slightly loose to a wire frame as shown in the figure. The frame is dipped into a soap solution and then taken out so that, the frame is completely covered with the film. When the portion $A$ of the film is punctured with a pin, the thread will,

• A. become convex towards $A$
• B. become concave towards $A$
• C. remain in the initial position
• D. either $\left(A\right)$ or $\left(B\right)$, depending on size of A w.r.t. $B$
  

Answer 1

The correct option is B become concave towards $A$

After the portion $A$ is punctured the shape of the thread will be as shown in the figure below.

Due to surface tension, the soap film $\left(B\right)$ will try to contract so as to occupy minimum surface area.
So, the thread will become concave towards $A$

Hence, $\left(B\right)$ is the correct answer.