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P. 4479. An easily moveable, insulated piston, of cross section A=2 dm2 and of mass m=5 kg, confines some air in a vertical thermally insulated cylinder. The air is heated by a heating element of power 200 W.

a) What is the speed of the piston?

b) By what amount does the internal energy of the air change in 2 s?

(5 points)

Deadline expired on 10 December 2012.

Google Translation (Sorry, the solution is published in Hungarian only.)

Megoldásvázlat. $\displaystyle a)$ $\displaystyle v=2{,}8$ cm/s.

$\displaystyle b)$ 286 J. Ez a fűtőszál által leadott energia 5/7-e, a többi a légkör ,,megemelésére" fordítódik.

Statistics on problem P. 4479.
 130 students sent a solution. 5 points: 73 students. 4 points: 14 students. 3 points: 11 students. 2 points: 7 students. 1 point: 20 students. 0 point: 3 students. Unfair, not evaluated: 2 solutions.

• Problems in Physics of KöMaL, November 2012

•  Támogatóink: Morgan Stanley