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Some pills against flu dissolve in water making it to fizz. At first the pill is on the bottom of the glass but after a while it rises to the surface. Why?

Lock is placed in a dam on a river in order for ships to be able to pass through. Assume the river has a flow rate of $Q=200m⁄s$ and that the lock connects places with height difference $H=4\;\mathrm{m}$ and has dimensions $s=100\;\mathrm{m}$, $d=20\;\mathrm{m}$. How many ships per day can this lock transport from the lower place to the higher place if the maximum flow rate in and out of the lock is $Q_{Z}=250m⁄s?$

• blood sedimentation

Given a test tube full of human blood, how long does it take for the red cells to settle at the bottom (the so called blood sedimentation)? The usual method for such a measurement is to let the blood cells settle for an hour and than to measure the height of the cells that are already at the bottom (usually about 10 mm). We are interested in an approximate calculation. You may need to use the Stoke's relation $F=6$ π η r v$ and the value of dynamical viscosity of blood plasma $η$ = 2 Ns/m²$$.

• different eyes

Aleš was sitting in a tram and the Sun was about 60° to the left. Because he was staring at a hot blond in front of him one of his eyes was in the shadow of his nose. When the blond noticed he was staring at her he turned his eyes to the right and he found out that he saw different color shades in each of his eyes. Describe the difference between the shades he observed with his left eye compared to his right eye. Why did this happen?

Design a shape for a sandglass so that the dependance of the height of sand on time is linear. If you do not neglect friction etc. you can gain some extra points.

Terka was playing around and spilled five liters of liquid nitrogen in her room. Couple days later she bought five liters of gasoline, brought it to her room and burned it. Could this playing around result in her being sick? To be more concrete describe the change in the temperature, pressure and oxygen concentration in her room (in both cases) if it is perfectly isolated and has dimensions 3$x3x4\;\mathrm{m}$.

• Dr. Nec.

There are two ways to measure the amount of wood in a pile of trees. Either as the volume of pure wood in the pile or as the volume of wood together with the empty spaces in the pile. Find the conversion factor between these two units assuming the trees are cylinders of radius $r$ that are layed one on top of the others.

• Bubbles.

A spherical cap of radius $r$ is made by blowing air into a circular surface of soap water. Estimate the velocity of air molecules hitting the surface?

There are many interesting properties of water that other liquids do not possess. Some of them are listed at http://www.btinternet.com/ martin.chaplin/anmlies.html. Think of some consequences of these anomalies for the life on Earth, humans and technology.

A solid sphere of density ρ is placed between two layers of immiscible liquids (see picture). Densities of the upper and lower liquids are ρ_{1} and ρ_{2} respectively. Assume that ρ_{1} ρ < ρ_{2}. Calculate the fraction of the sphere surrounded by the upper resp. lower liquid.

Two travelers, one fat and the other skinny, are arguing who would have better chances of surviving in extreme conditions. Tell them who will live longer in the following environments. Hot(50 °C), cold(-1 °C), after a boat accident in the Mediterranean sea, inside a hurricane, inside a heavy snow storm and in the middle of earthquake inside a city. Except of their body fat they are exactly the same. They even wear the same clothes and they do not carry anything else. Be original and remember that details matter.

In the middle of the Battle of Midway one of the Japanese pilots got thirsty. After searching the cockpit he found out that the supply management gave him only bottles with soda. What should he do in order to satisfy his thirst?