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 10 May 2012.