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Saitama
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Chestermiller said:
About your Method 1, Can we narrow down our region? What is the significance of having no vertical forces along the dotted lines?
Surface tension - thread in soap solution
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The discussion centers on calculating the force exerted by surface tension on a thread in a soap solution, specifically when considering the thread's interaction with a film. The participants explore the balance of forces, noting that the surface tension force is affected by the geometry of the thread and the film. They derive that the total force due to surface tension is 4TR, which must be balanced by the forces at the endpoints of the thread. Confusion arises regarding the calculations for different configurations, particularly when integrating the forces and determining the correct relationships between the variables. Ultimately, they arrive at the conclusion that T = πF/(2L) is the correct expression for tension in this scenario.
About your Method 1, Can we narrow down our region? What is the significance of having no vertical forces along the dotted lines?
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Pranav-Arora said:About your Method 1, Can we narrow down our region? What is the significance of having no vertical forces along the dotted lines?
I used as a free body the region of film and string between the dotted lines. There are only two vertical forces acting on this free body, the force F downward, and the force of the frame at the top (pointing upward). The force of the frame between the dotted lines (pointing upward), by Newton's third law, is the same as the force of surface tension between the dotted lines acting downward on the frame.
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