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Release date: Sept. 11th, 2020.
Last revision: Oct. 11th 2020.

All the problems, to stimulate a good discussion, have been formulated as open physics questions. That’s why the statement is never too stringent and it is assumed that every phenomenon will be studied both theoretically and experimentally (when possible) with dependence on all the most relevant parameters. More than that, there is not any general understanding of the task condition. If your interpretation of a certain problem condition corresponds to the written one and is interesting enough and your investigation is challenging and broad – the jury members will most likely award you with the nice marks. Surely, your team is not expected to spend years on every problem. So you should carefully consider your time budget and choose the most important and interesting parameters to study together with doing your best on both the theoretical model and experimental confirmation.

Nuclear mousetraps
An array of mousetraps and ping-pong balls results in a chain reaction. Construct a model for the macroscopic dynamics of such a system, identifying all relevant parameters, and determine the spatiotemporal behavior of the mousetrap excitation probability, and the threshold mousetrap density for the chain reaction to occur.

Pop-Pop away
The Pop-Pop boat is a small toy powered by a candle. Its engine is very simple, since it is just made of a boiler. Propose a boat design that maximizes the travelled distance using a tealight candle. Estimate the energy conversion efficiency of your boat.

Dirty racing
Investigate the distance a ball travels on a horizontal surface of wet sand before coming to rest if initially it was subjected to translational motion parallel to the surface. How does this distance depend on the ball material (wood, metal, rubber etc.), its initial velocity and other relevant parameters?

Hydraulic jump white hole
When a steady stream of water from a tap hits the sink, the water spreads in a circular disc bounded by a region where the water height is greater than its surroundings, as seen in the Figure. This so-called hydraulic jump is analogous to a white hole, the time-reversed version of a black hole, in the sense that surface waves cannot enter the disc against the flow, whilst there is a natural outward flow. Explain the physics behind the hydraulic jump, and how its properties can be matched to those of a white hole. Perform an experiment in order to verify the correspondence. Is it possible to make a hydraulic jump with liquids other than water? When does the white hole analogy break down?

Distant thunder
What parameters of thunder can one reconstruct from a photograph of lightning? How does the answer change if a silent video recording is used instead? Conversely, what parameters of lightning can one reconstruct from an audio recording of thunder?

The finger of death
Under some conditions, a stalactite of ice known as a brinicle can form underneath the frozen surface of an ocean. Reproduce the phenomenon on a laboratory or home scale, and study the brinicle growth rate and its final size.

Vegetable electricity
Some internet posts suggest that it is possible to generate electricity from photosynthesis by using a metallic network that winds through the roots of a plant. In response, a skeptic may claim that the setup is just a voltaic pile, and that therefore, photosynthesis is irrelevant. Explain the phenomenon and specifically determine whether photosynthesis is indeed involved. Determine the main factors affecting the phenomenon, and optimize them so as to generate the maximal power per unit of soil area.

Heavy parachute
Is it possible to build a magnetic parachute to protect a load from impact when landing on a non-magnetic metallic surface? How should it be built in order to minimize the impact damage? What are the limitations of your parachute?

Solar retraction motor
A solar retraction motor works by using the thermal shrinkage and relaxation of polyethylene or other materials. Investigate the maximal rotation speed and maximal power of these types of motors, and explore ways to maximize their efficiency using commonly found materials. How do these quantities scale with size of the motor?

Rolling pasta
When spaghetti is rehydrated on a wet cloth, the noodles gradually acquire a curvature that persists even when they are taken out to dry, and they will start moving with some velocity. Investigate the noodle movement and its shape dynamics. Is the phenomenon present for other common shapes of pasta, such as linguine, bucatini or lasagna?
https://youtu.be/NyewlvPgxxg

The spinning washer
A washer on a vertical steel rod may start spinning instead of simply sliding down. Study the motion of the washer, the sliding-spinning transition, and determine the terminal velocity.

Metallic forest
In the electrolysis of aqueous solutions of metal salts, fractal-like dendrites can begin to grow gradually on the electrodes. How can the dendrite shape and fractal dimension be controlled by choice and variation of the setup parameters?

Branching light
When a laser beam passes through a thin film (e.g., soap bubble film), random filaments of light are created by effect known as branch flow. Explain the phenomenon. Can one design a medium to produce specific branching patterns? Can it be extended to other wave phenomena (water waves or sound waves, etc.)?

Ice clock
An ice cube inside a mix of vegetable oil and baby oil will remain between the two liquids because of its density. As the ice cube melts and releases trapped bubbles, it goes up and down periodically in an intriguing way. Can this experiment be turned into a clock? What would be its longevity and precision? Optimize the setup parameters (shape, temperature, composition, length scales, etc.) to obtain the maximal clock precision.

Burning bottle cutter
It is possible to cut glass bottles into two pieces with a string using fire and cold water. What is the physics behind this effect, and how can one optimize it? Is it possible to cut out a shape in the glass that is more complex than a simple straight line?

Graphite lamp
Devise the most energy efficient lamp possible using the graphite rod from a pencil. Investigate how the intensity and duration of the light depend on the hardness of the graphite and other relevant parameters.
Quantum-droplet analogy
Small droplets on the surface of a vibrating liquid can exhibit quantum-like behavior in analogy with the so- called pilot wave theory. Construct an experiment to test as many quantum analogies as possible, and discuss the theoretical and experimental limitations of this analogy. Can the analogy be pushed to cover phenomena involving entanglement, such as Bell inequality violations?