Zadania 2002
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Heat engine
A tall glass cylinder is half-filled with hot water and topped up with cold water. A small ampule, containing a few drops of ether or alcohol (and closed off by a rubber pipette cap), is then put in. Describe the phenomena occurring in the system. How does the motion of the ampule change with time?
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Spider’s web
A spider’s thread looks like a string of pearls. What is the reason for this? Make experiments to investigate the relevant parameters.
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Flying colours
Why do flags flutter in the wind? Investigate experimentally the airflow pattern around a flag. Describe this behaviour.
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Hazy
The colour of a distant forest appears not green, but hazy blue. What is the minimum distance at which this phenomenon is observed? How do weather conditions affect this? Is it possible that a forest can appear grey?
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Pond-skater
It is known that unwettable small bodies can float on water due to the surface tension force. Construct a floating raft based on this principle and calculate its static and dynamic parameters.
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Stop and start
Sometimes a flow of traffic can experience sudden stops and starts for no apparent reason. Build a physical model to explain why this occurs.
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Ohm’s Law for a liquid
It is often said that electric current „flows“. Is this the only analogy between electric cur-rent and the flow of a liquid? Investigate theoretically and experimentally other analogies between these two things.
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Charged sand
Fine, well-dried quartz sand is poured out of a short thin tube into a conical metallic vessel connected to an electrometer. Investigate the behaviour of the sand stream as the vessel fills up. What changes if the stream is lit by a UV-lamp?
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Chromatography
Put a drop of coloured liquid on a piece of absorbent paper. Describe quantitatively the observed phenomena.
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Sound cart
Construct and demonstrate a device that can be propelled solely by sound. Investigate its properties.
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Equilibrium
Fill a glass with water up to the point where a convex meniscus is formed. Place a table tennis ball on the surface of the water. Investigate and explain the stability of its equilibrium. Repeat your experiment with other liquids?
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Electro-conductivity
How can you measure the electro-conductivity of salt solutions without using direct contact electrodes? Analyse the problem and demonstrate your device.
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Spinning ball
A steel ball of radius 2-3 cm is put on a horizontal plate. Invent and construct a device, which allows you to spin the ball at high angular velocity around a vertical axis. The device should have no mechanical contact with the ball.
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Torn sail
Determine the dependence of the efficiency of a sail (for instance, the drag coefficient) on its degree of perforation. What drag force would result if a fishing net is used as a sail?
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Pulsating air bubble
Trap an air bubble of radius 1-2 cm under an inverted watch glass beneath a water surface. Introduce alcohol into the bubble through a thin tube, controlling and adjusting the rate of flow until the bubble pulsates rhythmically. Study the phenomenon and explain your observations.
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Elastic pendulum
Study and describe the behaviour of a pendulum where the bob is connected to a spring or an elastic cord rather than to a stiff rod.
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Bottle battle
Take two opened glass bottles of cola and knock one against the other. After a short while, the cola spurts out of one of the bottles. Investigate and explain the phenomenon.
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