Question

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

• A. become concave toward side $A$
• B. become concave toward side $B$
• C. become straight
• D. remain as it is

Answer 1

The correct option is A become concave toward side $A$

Initially the surface tension is balanced at the boundary of two portions by both sides.
However, as portion $A$ is punctured then adhesive forces between thread and film dominates on the side $B$.
Thus, net surface tension is directed towards side $B$ which will make the thread concave towards side $A$.