Archív Turnaja Mladých Fyzikov

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Zadania 1998

  1. INVENT YOURSELF Construct an aeroplane from a sheet of paper (A4, 80 g/m2). Make it fly as far and/or as long as possible. Explain why it was impossible to reach a greater distance or a longer time.
  2. POPPING BODY A body is submerged in water. After release it will pop out of the water. How does the height of the pop above the water surface depend on the initial conditions (depth and other parameters)?
  3. SPINNING DISC Investigate and explain the phenomenon of a spinning annular disc as they progress down a straight, cylindrical rod. If the rod is moved upwards at a defined velocity, the disc spins at constant height. Investigate the mechanism.
  4. WATER STREAMS A can with three holes in the side-wall at the same height slightly above the bottom is filled with water. The water will escape in three separate streams. By gently touching the streams with a finger they may unite. Investigate the conditions for this to happen.
  5. WATER JET If a vertical water jet falls down onto a horizontal plate, standing waves will develop on the surface of the jet. Investigate the dependence of this phenomenon on different parameters.
  6. MOUNT EVEREST Can you see Mount Everest from Darjeeling?
  7. AIR BUBBLE An air bubble rises in a water-filled, vertical tube with inner diameter 3 to 5 mm. How does the velocity of the rising bubble depend on its shape and size?
  8. TRICK It is known that a glass filled with water and covered with a sheet of paper may be turned upside down without any loss of water. Find the minimum amount of water to perform the trick successfully.
  9. WOVEN TEXTILES Look at a point-like light source through different woven textiles. Describe what you see. What is the explanation of the phenomenon?
  10. REPEATED FREEZING While a vessel filled with an aqueous solution of a volatile fluid, e.g., ammonia, ethanol or acetone, is being cooled, repeated freezing and melting may be observed near the surface. Describe and explain the phenomenon.
  11. CURRENT SYSTEM In a Petri dish (shallow bowl), small metal balls, e.g., 2 mm in diameter, are immersed in a layer of castor oil. The inner rim of the dish contains an earthed metal ring. Above the centre of the dish there is a metal needle which does not touch the oil surface. Investigate what happens when the voltage between needle and earth is about 20 kV.

    Warning: The high voltage should be obtained by means of a safe generator, e.g., an electrostatic generator!

  12. POWDER CONDUCTIVITY Measure and explain the conductivity of a mixture of metallic and dielectric powders with various proportions of the two components
  13. ROPE How is it possible that a very long and strong rope can be produced from short fibers? Prepare a rope from fibers and investigate its tensile strength.
  14. WATER RISE Immerse the end of a textile strip in water. How fast does the water rise in the strip and what height does it reach? In which way do these results depend on the properties of the textile?
  15. LUMINESCENT SUGAR Investigate and explain the light produced when sugar crystals are pulverized. Are there other substances with the same property?
  16. STRANGE MOTION Make a mixture of ammonium nitrate and water, proportion 5 to 1. When the mixture is heated to about 100oC it melts. When it cools,it crystallizes and you may observe a strange motion below the surface. Investigate and explain the phenomenon.

    Safety rules: Do not heat the ammonium nitrate without water, preferably use a water bath! Use protection glasses during the experiment!

  17. ICICLES Investigate and explain the formation of icicles.
  1. VYNAJDI SA - INVENT YOURSELF Vytvor lietadlo z jedneho papiera (A4, 80 g/m2) tak, aby letelo co najdalej a/alebo co najdlhsie. Vysvetli, preco sa neda dosiahnut vacsia vzdialenost alebo dlhsi cas.
  2. VYSKAKUJUCE TELESO - POPPING BODY Teleso je ponorene vo vode. Po uvolneni teleso vyskoci von z vody. Ako zavisi vyska vyskoku nad hladinu vody od zaciatocnych podmienok (hlbka a ine parametre)?
  3. ROTUJUCI PRSTENEC - SPINNING DISC Prstenec sa otaca okolo valcovitej tyce a pri tom sa pohybuje smerom nadol. Ak je tyc posuvana smerom hore danou rychlostou, prstenec sa bude otacat v konstantnej vyske. Preskumaj a vysvetli tento mechanizmus.
  4. VODNE PRUDY - WATER STREAMS Plechovka s troma otvormi v bocnej stene v rovnakej vyske tesne nad dnom je naplnena vodou. Voda bude vytekat v troch oddelenych prudoch. Ak sa prstom jemne dotkneme tychto prudov, mozu sa spojit. Preskumaj podmienky, pre ktore sa toto stane.
  5. PRUD VODY - WATER JET Ak zvisly vodny prud tecie na vodorovnu platnu, na povrchu prudu sa vytvoria stojace vlny. Preskumaj zavislost tohto ukazu od roznych parametrov.
  6. MOUNT EVEREST Je mozne vidiet Mount Everest z Darjeeling-u?
  7. VZDUCHOVA BUBLINA - AIR BUBBLE Vzduchova bublina stupa vo vodou naplnenej zvislej trubici s vnutornym priemerom 3 az 5 mm. Ako za1visi rychlost stupania bubliny od jej tvaru a velkosti?
  8. TRIK - TRICK Je zname, ze pohar naplneny vodou a prikryty harkom papiera sa da otocit dolu hlavou bez toho, aby nejaka voda vytiekla. Najdi minimalne mnozstvo vody potrebne na to, aby sa tento pokus podaril.
  9. TKANA LATKA - WOVEN TEXTILES Pozri sa na bodovy zdroj svetla cez rozne druhy tkanych latok. Popis, co vidis. Ake je vysvetlenie tohto javu?
  10. OPAKOVANE MRZNUTIE - REPEATED FREEZING Pocas chladenia nadoby naplnenej vodnym roztokom prchavej tekutiny (napriklad amoniak, etanol alebo aceton) je mozne pri povrchu pozorovat opakovane zamrzanie a topenie. Popis a vysvetli tento jav.
  11. PRUDOVY SYSTEM - CURRENT SYSTEM V Petriho miske (plytka nadoba) su male kovove gulicky (napr. 2 mm v priemere), ponorene vo vrstve ricinoveho oleja. Na vnutornom okraji misky je umiestnena uzemnena kovova obruc. Nad stredom misky je kovova ihla, ktora sa nedotyka olejovej vrstvy. Preskumaj, co sa stane, ak napatie medzi ihlou a zemou je asi 20 kV.

    Upozornenie: Vysoke napatie sa da ziskat pouzitim bezpecneho generatora, napriklad elektrostatickeho.

  12. VODIVOST PRASKU - POWDER CONDUCTIVITY Odmeraj a vysvetli vodivost zmesi kovoveho a izolujuceho prasku s roznymi pomermi tychto dvoch zloziek.
  13. LANO - ROPE Ako je mozne, ze z kratkych vlakien sa da vyrobit velmi dlhe a pevne lano? Priprav lano z vlakien a preskumaj jeho pevnost v tahu.
  14. STUPANIE VODY - WATER RISE Ponor koniec pasika z latky do vody. Ako rychlo bude voda v pasiku stupat a aku maximalnu vysku dosiahne? V ktorom smere zavisia vysledky tohto pokusu od vlastnosti latky?
  15. SVIETIACI CUKOR - LUMINESCENT SUGAR Preskumaj a vysvetli svetlo vznikajuce pri drveni cukrovych krystalov na prasok. Existuju aj ine latky s rovnakou vlastnostou?
  16. ZVLASTNY POHYB - STRANGE MOTION Sprav zmes dusicnanu amonneho (ammonium nitrate) a vody, pomer 5:1. Ak tuto zmes zahrejeme na asi 100oC, zacne sa topit. Ked sa ochladzuje, krystalizuje a je mozne pozorovat zvlastny pohyb pod povrchom. Preskumaj a vysvetli tento jav.

    Bezpecnostne pokyny: Nezohrievaj zmes dusicnanu ammonneho bez vody, najlepsie je pouzit vodny kupel! Pouzi ochranne okuliare pocas experimentu!

  17. CENCULE - ICICLES Preskumaj a vysvetli proces tvorby cenculov.