Problems for the 14th
- Electrostatic motor
Is it possible to create a motor
which works by means of
an electrostatic field? If yes, suggest how it may
be constructed and estimate its parameters.
- Singing saw
Some people can play music
on a handsaw. How do they get
different pitches? Give a quantitative
description of the phenomenon.
- Tuning dropper
Make the music resonator shown in the
picture. Investigate the conditions that affect the pitch. Can you observe
amplification of external sounds? If yes, how
can you explain this?
- Dancing sand clock
Investigate the trickling of sand when a sand clock
(egg-timer) is placed on a vibrating base.
- Rubber heat machine
Investigate the conversion of energy in the process of deformation of rubber. Construct a heat machine, which uses rubber as the working element and demonstrate how it works.
- Fractal diffraction
Produce, demonstrate and analyse diffraction pictures of fractal structures of different orders.
When drying a starch solution,
you will see cracks forming. Investigate and explain this phenomenon.
Two electrodes of different metal are immersed in an electrolyte solution. Investigate the dependence of the measured
potential difference on the relative
motion of electrodes and their shapes.
- Pouring out
Investigate how to empty a
bottle filled with a liquid
as fast as possible, without external technical devices.
- Water stream pump
Construct and demonstrate a water stream vacuum pump. What is your
record value for the minimum
- Rolling balls
Place two equal balls in a horizontal,
V-shaped channel, with the walls
at 90 degrees to each other,
and let the balls roll towards each other. Investigate and explain the motion of the balls after the collision. Make experiments with several different kinds of ball
pairs and explain the results.
Make an aqueous solution of gelatine (10g gelatine in 90ml of
water), heat it to 80 degrees
C in a water bath
and mix it with a
solution of potassium iodide. Pour the solution
in a test tube and cool it.
Pour a solution of copper sulphate on the surface
of the gel. Find a physical explanation to the observed phenomena.
- Membrane electrolyser
In an electrolyser, containing a membrane which completely divides the space between two inert electrodes, the pH-value of the diluted salt solution will change substantially after electrolysis. Investigate how this difference
depends on the pore size
of the membrane.
- Thread dropper
One end of a thread
is immersed in a vessel
filled with water. The other end hangs down outside without contact with the outer wall of the
vessel. Under certain conditions, one can observe
drops on that end of
the thread. What are those
conditions? Determine how the time
of appearance of the first
drop depends on relevant parameters.
- Bubbles in magnetic
Observe the influence of an alternating magnetic field (50 or 60 Hz) on the kinetics
of gas bubbles in a vessel filled
with water. The bubbles can be generated
by blowing air into the
- Adhesive tape
Investigate and explain the light produced, when adhesive tape is ripped
from a smooth surface.
Seiching is a phenomenon shown by long
and narrow deep lakes. Due to changes
in atmospheric pressure, the water of the
lake can start moving in such a
way that its level at both ends
of the lake makes periodic motions, which are identical, but out of phase.
Make a model that predicts the period of seiching (depending on appropriate parameters) and test its validity.