These are official problems for 12th International Young Physicists Tournament, Vienna, 1999. These problems are dated November 29, 1998. Translation into slovak was done by author of this page.

# Problems for 12th IYPT '99

1. ROTATION
A long rod, partially and vertically immersed in a liquid, rotates about its axis. For some liquids this will cause an upward motion of the liquid on the rod and for other liquids a downward motion. Explain this phenomenon and determine the essential parameters on which it depends.

2. IONIC MOTOR
An electrolyte (an aqueous solution of CuSO4, NaCl, ...) in a shallow tray is made to rotate in the field of a permanent magnet (a small "pill" placed under the tray). The electric field is applied from a 4.5V battery in such a way that one electrode is in the form of a conducting ring immersed in the electrolyte - the other is a tip of wire placed vertically in the center of the ring. Study the phenomenon and find possible relations between the variables.

3. MAGIC MOTOR
Construct a DC motor without a commutator, using a battery, a permanent magnet and a coil. Explain how it functions.

4. SOAP FILM
Explain the appereance and development of colours in a soap film, arranged in different geometries.

5. DROPPED PAPER
If a rectangular piece of paper is dropped from a height of a couple of meters, it will rotate around its long axis whilst sliding down at a certain angle. How does this angle depend on various parameters?

6. SINGING GLASS
When rubbing the rim of a glass containing a liquid a tone can be heard. The same happens if the glass is immersed in a liquid. How does the pitch of the tone depend on different parameters?

7. HEATED NEEDLE
A needle hangs on a thin wire. When approached by a magnet the needle will be attracted. When heated the needle it will return to its original position. After a while the needle will be attracted again. Investigate this phenomenon, describe the characteristics and determine the relevant parameters.

8. ENERGY CONVERTER
A body of mass 1 kg falls from a height of 1 m. Convert as much possible of the released potential energy into electric energy and use that to charge a capacitor of 100µF.

9. AIR DRYER
During 4 minutes collect as much water as possible from the air in the room. The mass of the equipment must not exceed 1kg. The water should be collected in a glass test tube, provided by the jury.

10. CHARGED BALLOON
An air-filled balloon rubbed with wool or dry paper may stick to the ceiling and stay there. Investigate this phenomenon and measure the charge distribution on the surface of the balloon.

11. BILLIARD
Before a snooker game starts, 15 balls form an equilateral triangle on the table. Under waht conditions will the impact of the white ball (16th ball) produce the largest disorder of the balls?

12. FLOUR CRATERS
If you drop a small object in flour, the impact will produce a surface structure which looks like moon crater. What information about the object can be deduced from the crater?

13. GAS FLOW
Measure the speed distribution of the gas flow in and around the flame of a candle. What conclusions can be drawn from the measurements?

14. WHEAT WAVES
The wind blowing through a wheat field creates waves. Describe the mechanism of wave formation and discuss the parameters which determine the wavelength.

15. BRIGHT SPOTS
Bright spots can be seen on dew drops if you look at them from different angles. Discuss this phenomenon in terms of the number of spots, their location and angle of observation.

16. LIQUID DIODE
Make an electrochemical diode and investigate its properties, in particular the frequency dependece.

17. SOUND FROM WATER
When you heat water in a kettle you hear a sound from the kettle before tha water starts to boil. Investigate and explain this phenomenon.

# Zadania pre 12. TMF (Slovenska verzia)

1. ROTACIA
Dlha zvisla tyc, ciastocne ponorena do kvapaliny, sa otaca okolo svojej osi. Pre niektore kvapaliny to sposobi pohyb kvapaliny pri tyci smerom hore, pre ine kvapaliny pohyb smerom dole. Vysvetli tento jav a zisti dolezite parametre, od ktorych tento jav zavisi.

2. IONOVY MOTOR
Elektrolyt (vodny roztok CuSO4, NaCl, ...) v plytkej nadobe je uvedeny do rotacneho pohybu v poli permanentneho magnetu (mala pilulka umiestnena pod nadobou). Elektricke pole je vytvarane 4.5V bateriou tak, ze jedna elektroda je tvorena vodivym prstencom ponorenym do elektrolytu, druhou je koniec drotu umiestneny zvislo v strede prstenca. Prestuduj tento jav a najdi mozne vztahy medzi parametrami.

3. ZAZRACNY MOTOR
Zostroj jednosmerny motor bez komutatora, pomocou baterie, permanentneho magnetu a cievky. Vysvetli, ako funguje.

4. MYDLOVA BLANA
Vysvetli vyvin a vyzor farieb na mydlovej blane, ktora zaujme rozne usporiadania.

5. PUSTENY PAPIER
Ak obdlznikovy kus papiera pustime z vysky niekolkych metrov, bude rotovat okolo svojej dlhsej osi a zaroven klzat dole pod istym uhlom. Ako zavisi tento uhol od roznych parametrov?

6. SPIEVAJUCI POHAR
Ked suchame okraj pohara, ktory obsahuje kvapalinu, mozeme pocut ton. To iste sa deje aj v pripade, ze je pohar ponoreny v kvapaline. Ako zavisi vyska tonu od roznych parametrov?

7. OHRIEVANIE IHLY
Ihla je zavesena na tenkom drote. Ked k ihle priblizime magnet, ihla sa k nemu pritiahne. Po zohriati ihly sa tato vrati do svojej povodnej polohy. Po chvili bude ihla znovu pritiahnuta k magnetu. Preskumaj tento jav, popis jeho charakteristiky a rozhodni o dolezitych parametroch.

8. PREMIENAC ENERGIE
Teleso hmotnosti 1kg pada z vysky 1m. Premen co najviac z uvolnenej potencialnej energie na elektricku energiu a pouzi ju na nabitie kondenzatora s kapacitou 100µF.

9. SUSICKA VZDUCHU
Pocas 4 minut zhromazdi co najviac vody zo vzduchu v miestnosti. Hmotnost zariadenia nesmie prekrocit 1kg. Voda bude zhromazdovana v sklenenej skumavke, ktoru poskytne porota.

10. NABITY BALON
Vzduchom naplneny balon treny vlnou alebo suchym papierom mozeme "prilepit" na strop a balon ostane tam. Preskumaj tento jav a zmeraj rozlozenie naboja na porchu balona.

11. BILLIARD
Pred zaciatkon hry je na stole 15 guli, ktore tvoria rovnostranny trojuholnik. Pri akych podmienkach sposobi uder bielej (16-tej) gule najchaotickejsie usporiadanie?

12. MUCNE KRATERY
Ak pustime maly predmet do muky, jeho dopad vytvori v muke povrchovu strukturu, ktora vyzera ako mesacny krater. Ake informacie o predmete sa daju vydedukovat z kratera?

13. TOK PLYNU
Zmeraj rozlozenie rychlosti toku plynu v a okolo plamena sviecky. Ake zavery mozno vyvodit z tychto merani?

14. PSENICNE VLNY
Vietor fukajuci ponad psenicne pole vytvara vlny. Popis mechanizmus tvorby vln a rozober parametre, ktore urcuju vlnovu dlzku.

15. SVETLE BODY
Svetle body mozeme vidiet na kvapkach rosy, ak sa na ne pozerame z roznych uhlov. Rozober tento jav s ohladom na pocet bodov, ich umiestnenie a uhol pozorovania.

16. TEKUTA DIODA
Vytvor elektrochemicku diodu a preskumaj jej vlastnosti, hlavne frekvencnu zavislost.

17. ZVUK Z VODY
Ked zohrievame vodu v konvici, mozeme pocut zvuk z konvice predtym, ako zacne voda vriet. Preskumaj a vysvetli tento jav.