Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
Already signed up?
New to KöMaL?

Problem P. 4479. (November 2012)

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 pont)

Deadline expired on December 10, 2012.

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

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.


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