Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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# Problem P. 3795. (April 2005)

P. 3795. We have to cool down a 5 kg copper block of a temperature of 300 oC to the temperature of 30 oC. We can use 20 oC water for the cooling supplied at an arbitrary rate. At what rate is the cooling water to be used so that the smallest possible amount of water is used for the cooling? How much is this quantity? (Let us assume that the temperature of the copper block changes only as a result of the effect of the water poured on it.)

(5 pont)

Deadline expired on May 11, 2005.

### Statistics:

 82 students sent a solution. 5 points: Domonkos Tamás, Dudás János, Gyenis András, Kocsis Vilmos, Lantos Judit, Lapis Leonárd, Máté István Mátyás, Matyó Márió, Meszéna Balázs, Nagy 317 Péter, Pálinkás Csaba, Pásztor 001 Attila, Peregi Tamás, Pósa László, Széchenyi Gábor, Szentandrási István, Szilágyi Zsombor, Szolnoki Lénárd, Takátsy Balázs, Tüzes Dániel. 4 points: Hujter Mónika, Remes Bálint, Soós 989 János. 3 points: 35 students. 2 points: 9 students. 1 point: 6 students. 0 point: 9 students.

Problems in Physics of KöMaL, April 2005