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### 1. Series 35. Year - 2. two-second rule

The two-second rule is a driving principle which states that a safe time distance between two vehicles is at least two seconds long. Suppose a traffic junction where a $n_1$-lane road changes into a $n_2$-lane one. The maximum allowed speed in the first section is $v_1$. What is the lowest possible maximum speed $v_2$ that can be allowed in the second section so that there is no traffic jam and everyone can follow the two-second rule? The average length of a car is $l$ and it can change its speed in leaps.

### 1. Series 35. Year - P. so hot

You may have noticed that not all volcanos on Earth have the same „universal“ shape – they differ from each other. For example, compare the photos of the Hawaiian volcano Mauna Loa and the Italian Vesuvio. They differ not only in the steepness of their walls but also in the style of eruptions. Both of these properties are related to the viscosity of magma. Discuss the effect of the viscosity of magma on the style and dangerousness of eruptions. Is is related to the geographic location of the volcanoes?

### 6. Series 34. Year - E. spilled glass

Take a glass, can or any other cylindrically symmetrical container. Measure the relationship between the angle of inclination of the container when it tips over and the amount of water inside of it. We recommend to use a container with greater ratio of its height to the diameter of its base.

Jindra was watering the table.

### 2. Series 34. Year - P. costly ice hockey

Estimate how much the complete glaciation of an ice hockey rink costs.

Danka doesn't like ice hockey, but she likes figure skating.

### 6. Series 33. Year - S.

We are sorry. This type of task is not translated to English.

### 4. Series 33. Year - P. climate changes feat. airplanes

Travel by airplane affects the atmosphere not only by well-known carbon emissions. Discuss how the aircraft industry affects warming of the atmosphere of Earth.

### 2. Series 33. Year - S.

We are sorry. This type of task is not translated to English.

### 1. Series 33. Year - P. planet destroyer

How small could a weapon capable of destroying a planet be? We are interested in the smallest and the lightest such weapons. The process should be reasonably fast, at least shorter than a human lifetime, and the faster it is, the better.

Karel watches sci-fi too much, this time the intro of Men in Black II.

### 1. Series 33. Year - S. slow start-up

We are sorry. This type of task is not translated to English.

Karel wants to have the longest problem assignment.

### 5. Series 32. Year - 2. warm reachability into the ball

Imagine you have subcooled homogeneous metal ball that you have just taken out of a freezer set to very low temperature. You want to find out how fast the ball temperature will increase if you put it in a warm room. It would be a university-level problem. Because of that, we made it easier for you. We ask about how deep into the ball will the „warm area“ reach. You can estimate it using dimensional analysis. We know relevant parameters of the ball - its density $\left [ \rho \right ] = \jd {kg.m^{-3}}$, specific heat capacity $\left [c\right ] = \jd {J.kg^{-1}.K^{-1}}$, thermal conductivity of the ball $\left [ \lambda \right ] = \jd {W.m^{-1}.K^{-1}}$ and we are interested in dependence on time $\left [t\right ] = \jd {s}$.

Karel inspired himself by a problem from Eötvös Competition.