Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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# Problem P. 4791. (December 2015)

P. 4791. Recently Peter's boiler makes very strange sounds, as if it would explode at any moment. A repairman was asked to have a look, and he said that limescale has deposited in the tube, and it must be descaled. Peter's small brother asked Peter how the strange sound could arise, and why the thermometer, which measures the temperature of the water, is scaled up to $\displaystyle 120~{}^\circ$C, since at that temperature the water would boil. What fraction of the tube is closed by the deposited scale?

What did Peter answer to these questions?

Data: The temperature of the water in the tube is $\displaystyle 80~{}^\circ$C, the pressure gauge reads 1.2 bar (excess) pressure, and at normal working conditions the pump makes the water flow at a speed of 3 m/s.

(6 pont)

Deadline expired on January 11, 2016.

### Statistics:

 25 students sent a solution. 6 points: Asztalos Bogdán, Balogh Menyhért, Blum Balázs, Csorba Benjámin, Forrai Botond, Kasza Bence, Kovács Péter Tamás, Sal Kristóf, Szick Dániel, Tomcsányi Gergely. 5 points: Csenger Géza, Csuha Boglárka, Kardos Réka, Krasznai Anna, Németh Csaba Tibor, Németh Flóra Boróka, Tófalusi Ádám. 4 points: 2 students. 3 points: 4 students. 2 points: 2 students.

Problems in Physics of KöMaL, December 2015