Only Conceptual Thinkers Can Solve This Soap Film Question | Pathfinder 9.2.7 скачать в хорошем качестве

Only Conceptual Thinkers Can Solve This Soap Film Question | Pathfinder 9.2.7

In this Physics video in Hindi for the chapter : "Mechanical Properties of Fluids" of Class 11, we discussed problem no. 9.2.7 from the book 'Pathfinder for Olympiad & JEE Advanced Physics'. Question : A film of a soap solution created in a loop formed by a rectangular wire frame and an inextensible light thread AB of length l, pulls the thread in the shape of a semicircle. If a force F applied at midpoint of the thread perpendicular to line segment AB turns the wire into two semicircles as shown in the figure, calculate surface tension of the soap solution. 👇 👇 👇 👇 👇 👇 Related Playlists 👇 👇 👇 👇 👇 👇 👇 👇 👇 Playlist on : Fluids - Pathfinder    • Fluids : Pathfinder   Playlist on : JEE Advanced PYQ (Mechanical Properties of Fluids)    • Fluids : JEE Advanced PYQ   ☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️☝️ This problem is a classic and conceptually rich question from Mechanical Properties of Fluids that directly tests understanding of surface tension, force balance, and symmetry, making it extremely important for aspirants of IIT-JEE Advanced. In the video, we begin by carefully visualizing the soap film formed within the rectangular frame and how the film exerts a pulling effect on the light thread due to surface tension. The initial equilibrium configuration, where the thread takes the shape of a semicircle, is discussed to highlight the uniform nature of surface tension acting along the length of the thread. We then analyze the situation when an external force is applied at the midpoint of the thread perpendicular to AB, causing the system to deform into two semicircles. The method of solution focuses on identifying all forces acting on the thread, especially the tangential forces due to the soap film on both sides, and balancing them with the applied force to determine the surface tension. The reasoning is purely conceptual and symmetry-based, avoiding unnecessary mathematical complexity, which is exactly the approach expected in IIT-JEE Advanced. Such problems are frequently included in Pathfinder Olympiad because they test deep physical intuition rather than routine calculation. The video clearly explains how surface tension acts along a line and how curved boundaries naturally arise due to uniform tension. Repeated practice of Pathfinder Olympiad problems like this strengthens understanding of Mechanical Properties of Fluids and builds confidence for IIT-JEE Advanced. The discussion emphasizes why Mechanical Properties of Fluids is a high-scoring yet subtle chapter, and why problems from Pathfinder Olympiad are invaluable for mastering it for IIT-JEE Advanced. Surface tension is defined as the property of a liquid surface by virtue of which it tends to minimize its surface area and behaves like a stretched elastic membrane. In this problem, surface tension of the soap solution is responsible for pulling the thread into curved shapes and opposing the externally applied force. Force is defined as an interaction that can change the shape or state of motion of a body. Here, the externally applied force at the midpoint of the thread balances the inward pull due to surface tension, allowing us to determine the magnitude of the surface tension. The principle of equilibrium states that when a system is at rest, the vector sum of all forces acting on it is zero. This principle is applied to the thread to balance the forces due to surface tension and the applied force, forming the basis of the solution to this Pathfinder Olympiad problem and making it highly relevant for IIT-JEE Advanced. The principle of symmetry states that in a symmetric physical configuration, forces and effects are equally distributed in corresponding directions. This theorem is used in this problem to argue that the soap film pulls the thread equally on both sides, simplifying the force balance and enabling an elegant solution. Such symmetry-based reasoning is frequently emphasized in Pathfinder Olympiad and is crucial for solving advanced questions in Mechanical Properties of Fluids for IIT-JEE Advanced. #jeeadvanced #fluid #surfacetension #tension