Problems for the 15th IYPT
1. Heat engine
A tall glass cylinder is half-filled
with hot water and topped up with cold water. A small ampoule, 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 ampoule change with time?
2. Spider's web
spider's thread looks like a string of pearls. What is the reason for
this? Make experiments to investigate the relevant parameters.
Why do flags flutter in the wind? Investigate
experimentally the airflow pattern around a flag. Describe this
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?
5. Pond skater
known that unwettable small bodies can float on water due to the surface
tension force. Construct a floating raft based on this principle and
determine its static and dynamic parameters.
6. Stop and
Sometimes a flow of traffic can experience sudden stops and
starts for no apparent reason. Build a physical model to explain why this
7. Ohm's Law for a liquid
It is said that electric
current “flows”. Is this the only analogy between electric current and the
flow of a liquid? Investigate theoretically and experimentally other
analogies between these two.
8. Charged sand
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
Put a drop of coloured liquid on a
piece of absorbant paper. Describe quantitatively the observed
10. Sound cart
Construct and demonstrate a device
that can be propelled solely by sound. Investigate its
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.
How can you measure the electroconductivity of salt
solutions without using direct contact electrodes? Analyse the problem and
demonstrate your device.
13. Spinning ball
A steel ball of
diameter 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
14. Torn sail
Determine the dependence of the efficiency
of a sail on its degree of perforation. What would be the effect of using
a fishing net as a sail?
15. 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
16. 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.
17. Bottle battle
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.