Problem P. 4443. (April 2012)
P. 4443. A soap film of surface tension is created in the frame, shown in the figure. The diameter of the frame is . A piece of unstretched hair of length , and of young modulus E joins the points P and Q. By what amount will the hair be elongated if the film in the right hand side is pricked by a hot pin. (The two endpoints of the hair are fixed and its weight is negligible. For small angles use the approximation: sin -3/6.)
Deadline expired on May 10, 2012.
Sorry, the solution is available only in Hungarian. Google translation
Megoldásvázlat. A megnyúlás