Mathematical and Physical Journal
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Problem P. 4521. (March 2013)

P. 4521. A sample of air of volume V1=3 dm3 and of pressure p1=6.104 Pa is confined to a fixed vertical cylinder which is closed at its bottom by a piston of cross section A=1 dm2, which can move frictionlessly. The piston is connected to the closed end of the cylinder with a spring, designed for both compression and tension, of length L0=0.6 m and of spring constant D=1000 N/m. The system is in equilibrium in this position. The external air pressure is p0=105 Pa.

a) Find the mass of the piston.

b) The air in the piston is heated slowly. How much heat must be added to the confined air in order to reach that state when the spring does not exert any force on the piston?

(4 pont)

Deadline expired on April 10, 2013.

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

Megoldásvázlat. $\displaystyle a)$ $\displaystyle m\approx 10$ kg.

$\displaystyle b)$ A gáz által végzett munka $\displaystyle 225~$J, a belső energia változása $\displaystyle \Delta E=900~$J, a közölt hő $\displaystyle Q=1125~$J.

Statistics:

 102 students sent a solution. 4 points: Antalicz Balázs, Asztalos Bogdán, Balogh Menyhért, Berta Dénes, Bingler Arnold, Blum Balázs, Bognár Tamás, Bősze Zsófia, Büki Máté, Csáky Pál, Csathó Botond, Cseuz Áron, Dávid Bence, Demeter Dániel, Epinger Bálint, Farkas Tamás, Fekete Panna, Filep Gábor, Fonyó Viktória, Forrai Botond, Garami Anna, Gróf Viktória, Holczer András, Horváth András Levente, Janzer Barnabás, Jenei Márk, Kacz Dániel, Kaprinai Balázs, Kenderes Anett, Krokos Ádám László, Lévai 482 Nikolett, Mihály 930 Ákos, Morvay Bálint, Olosz Balázs, Öreg Botond, Pázmán Zalán, Reitz Angéla, Sal Kristóf, Sárvári Péter, Seress Dániel, Sisák Mária Anna, Takács 737 Gábor, Tarjányi 158 Dániel, Trócsányi Péter, Varju Ákos, Vasvári Ádám Viktor, Virágh Anna. 3 points: 11 students. 2 points: 39 students. 1 point: 1 student. 0 point: 4 students.

Problems in Physics of KöMaL, March 2013