From IYPT

Historic Problems

For all past problems, please visit the IYPT Archive

Problems for the 31st IYPT 2018

Released by the IOC on July 13th, 2017

Please refer to the official and signed pdf as the authoritative source, that also includes pictures.

Any suggestion for a new IYPT Problem? Propose here.


The originator of a new concept finds, as a rule, that it is much more difficult to find out

why other people do not understand him, than it was to discover the new truth.

Hermann von Helmholtz

1. Invent Yourself

Construct a simple seismograph that amplifies a local disturbance by mechanical, optical or electrical methods. Determine the typical response curve of your device and investigate the parameters of the damping constant. What is the maximum amplification that you can achieve?

2. Colour of Powders

If a coloured material is ground to a powder, in some cases the resulting powder may have a different colour to that of the original material. Investigate how the degree of grinding affects the apparent colour of the powder.

3. Dancing Coin

Take a strongly cooled bottle and put a coin on its neck. Over time you will hear a noise and see movements of the coin. Explain this phenomenon and investigate how the relevant parameters affect the dance.

4. Heron's Fountain

Construct a Heron’s fountain and explain how it works. Investigate how the relevant parameters affect the height of the water jet.

5. Drinking Straw

When a drinking straw is placed in a glass of carbonated drink, it can rise up, sometimes toppling over the edge of the glass. Investigate and explain the motion of the straw and determine the conditions under which the straw will topple.

6. Ring Oiler

An oiled horizontal cylindrical shaft rotates around its axis at constant speed. Make a ring from a cardboard disc with the inner diameter roughly twice the diameter of the shaft and put the ring on the shaft. Depending on the tilt of the ring, it can travel along the shaft in either direction. Investigate the phenomenon.

7. Conical Piles

Non-adhesive granular materials can be poured such that they form a cone-like pile. Investigate the parameters that affect the formation of the cone and the angle it makes with the ground.

8. Cusps in a Cylinder

A horizontal cylinder is partially filled with a viscous fluid. When the cylinder is rotated around its axis, unusual fluid behaviour can be observed, such as cusp-like shapes on the walls of the cylinder. Investigate the phenomenon.

9. Candle in Water

Add some weight to a candle such that it barely floats in water. As the candle burns, it may continue to float. Investigate and explain this phenomenon.

10. Tesla Valve

A Tesla valve is a fixed-geometry, passive, one-direction valve. A Tesla valve offers a resistance to flow that is much greater in one direction compared to the other. Create such a Tesla valve and investigate its relevant parameters.

11. Azimuthal-Radial Pendulum

Fix one end of a horizontal elastic rod to a rigid stand. Support the other end of the rod with a taut string to avoid vertical deflection and suspend a bob from it on another string (see figure). In the resulting pendulum the radial oscillations (parallel to the rod) can spontaneously convert into azimuthal oscillations (perpendicular to the rod) and vice versa. Investigate the phenomenon.

12. Curie Point Engine

Make a nickel disc that can rotate freely around its axis. Place a magnet near the edge of the disc and heat this side of it. The disc starts to rotate. Investigate the parameters affecting the rotation and optimize the design for a steady motion.

13. Weighing Time

It is commonly known that an hourglass changes its weight (as measured by a scale) while flowing. Investigate this phenomenon.

14. Radiant Lantern

When taking a picture of a glowing lantern at night, a number of rays emanating from the centre of the lantern may appear in the pictures. Explain and investigate this phenomenon.

15. Blowing Bubbles

When blowing on a soap film in a ring, a bubble may be formed. The liquid film may pop or continue to exist. Investigate how the number of bubbles produced from a single soap film and the characteristics of the bubbles depend on the relevant parameters.

16. Acoustic Levitation

Small objects can levitate in acoustic standing waves. Investigate the phenomenon. To what extent can you manipulate the objects?

17. Water Bottle

The current craze of water bottle flipping involves launching a partially filled plastic bottle into the air so that it performs a somersault before landing on a horizontal surface in a stable, upright position. Investigate the phenomenon and determine the parameters that will result in a successful flip.


Authors: John Balcombe, Samuel Byland, Nikita Chernikov, Kent Hogan, Mihály Hömöstrei, Dina Izadi, Andrei Klishin, Frantisek Kundracik, Ilya Martchenko, Florian Ostermaier, Jelena Pajovic, Kerry Parker, Carmen Parton, Oksana Pshenichko, Igor Timoshchenko, Lise


Problem selection committee: John Balcombe, Samuel Byland, Ilya Martchenko


Epigraph selected by Evgeny Yunosov


Call for problem proposals

To participate in the IYPT, teams have almost a year to prepare so-called "Reports" on 17 tasks, called "problems".

If you have an idea for a new exciting IYPT problem, send your suggestion using the following this google form.

A committee was founded to work on the proposals submitted. After a special vote, they will prepare a set of best problems with improved wording and with all fields of physics represented. In case of need the committee might contact experts and the authors of the problems and ask for further information.

During the IOC meeting, we will discuss the proposals and make final decision about the set of problems.