1. Invent yourself
Propose a cycle of demonstrations and experiments that can help to explain and visually demonstrate the physical nature of sound waves and the properties of sound.

2. Fortune teller
When molten paraffin is made to drip from a candle into a saucer with water, different solidified shapes are obtained, like a “lens”, a “boat”, an “inkblot”. Study the shape of the solidified droplets in dependence of altitude of their fall.

3. Geyser
A strong ceramic resistor in the shape of a hollow cylinder is placed into water so that the axis of the cylinder is vertical, and the top plane is slightly below the water level. If electric current is passed through the resistor, the resistor, just like a geyser, periodically ejects portions of hot water upwards. Calculate and study experimentally the dependence of the eruption periods of the “geyser” on the power consumed by the resistor from the power supply unit.

4. Self excitation
A strong hum sometimes happens on the concerts of newbie rock bands, when the microphone appears close to the speaker that reproduces the signals amplified from this very microphone. How do the frequency and the amplitude of the produced sound oscillations depend on the distance between the microphone and the speaker, and on their mutual orientation?

5. Cosmic monument
A particular supercivilization is eager to create a cosmic monument, an isolated planetary system of three planets, of which one should move along a trajectory close to an equilateral triangle. What mutual ratios of masses and of velocities for planets would you recommend? Develop also a project for a nearly square-shaped orbit.

Construct a device that measures the level of radiation. Use it to locate the major sources of radiation in everyday life.

7. Runner
Estimate the maximum speed that a person can run with. Compare it with the experimental values. In your opinion, what will be the world record in 100 m sprint in the year 2000?

8. Photograph of a television screen
The motion of a camera’s shutter and its speed may be studied through taking photographs of a television image. With this technique, measure the exposure time of your camera and the speed of the shutter.

9. Passive motor
An apple dropped from a balcony of a multi-storey building will calmly descend into the hands of your friend, if you attach to the apple a propeller cut out of dense paper. Explain the principle of work for such a parachute and study the dependence of the drag force on the descent rate and on the sizes of the propeller’s blades.

10. Blowgun
A small knitting needle, with two rounded pieces of polyurethane foam strung onto it, is shot out of a blowgun. Find the optimal blowpipe size to shoot such a projectile. What maximum projectile speed did you succeed to achieve?

11. Gold cube
A cubic planet of pure gold evolves around the Sun and keeps one of its facets turned towards it. Estimate the difference of temperatures of the planet facets.

12. Little boat
A light little boat floats on the surface of a liquid electrolyte. When electric current is passed through the electrolyte, the boat starts moving. Estimate the speed of the boat.

13. Wooden cube
A cube is cut out of a single piece of wood. The edge of the cube is much smaller than the diameter of the tree trunk from which it was cut out. Propose a method to determine the direction of wood fibers in the cube (the positive orientation of fibers is from the roots to the top of the tree.)

14. Moon
Determine experimentally the ratio of brightnesses (illuminances) of sunlit and dark sides of the Moon at different lunar phases. Compare them with the theoretical estimations.

15. Glider
Construct a glider that is driven by a piece of soap. Your glider must win in two competitions: in racing against time for a distance of 50 cm and in floating for a longest range in a given direction (separate gliders may be constructed for each competition.) The linear dimensions of the glider may not exceed 6.28 cm. In the second competition, the glider may not carry more than 0.5 g of soap.

16. Sunset
The Sun becomes red at sunset. What are the colors of the Moon, of Venus and of a bright star when they are they are low on the horizon?

17. Epigraph
In our opinion, the epigraph to the Tournament problems may serve as a basis for serious researches as well as for excellent jokes. We expect both of these from you.