Problem P. 4443. (April 2012)

P. 4443. A soap film of surface tension $\sigma$ is created in the frame, shown in the figure. The diameter of the frame is $\ell$ . A piece of unstretched hair of length $\ell$ , 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 $\alpha$ $\approx$ $\alpha$ - $\alpha$ ³/6.)

(6 pont)

Deadline expired on May 10, 2012.

Sorry, the solution is available only in Hungarian. Google translation

Megoldásvázlat. A megnyúlás

$\Delta \ell=\frac{\ell}{6}\left(\frac{6\ell\sigma}{EA} \right)^{\frac{2}{3}}.$

Statistics:

13 students sent a solution.

6 points: Szabó 928 Attila.

5 points: Barta Szilveszter Marcell, Czipó Bence, Juhász Péter, Koncz Gabriella, Papp Roland, Sárvári Péter, Szélig Áron, Trócsányi Péter, Vajda Balázs.

4 points: 3 students.

Problems in Physics of KöMaL, April 2012

13 students sent a solution.
6 points:	Szabó 928 Attila.
5 points:	Barta Szilveszter Marcell, Czipó Bence, Juhász Péter, Koncz Gabriella, Papp Roland, Sárvári Péter, Szélig Áron, Trócsányi Péter, Vajda Balázs.
4 points:	3 students.

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