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## gas mechanics

### 5. Series 21. Year - P. Rama-quake

Finally you got onto the surface of Rama. Suddenly it started to shake and you think the rotation speed has changed. How you can measure the rotation speed? Can you find more than one experiment?

Martin Formánek

### 2. Series 21. Year - 1. a spit

You travel in fast train and are looking outside of the open window. Three windows in front of you someone spits a chewing-gum. How long do you have to get back to coupe to avoid contact with chewing-gum? The chewing-gum is spherical shape and was not thrown out, but just laid in air flow.

Roman Fiala.

### 2. Series 21. Year - 2. a car in the rain

Calculate a slope of front glass of a car, so that water drops at speed 80 km ⁄ h do not run off, but to the sides. Verify that you results is compatible with reality. What else influence the slope of front window?

Nad problémem se zamýšlel Honza Prachař při jízdě autem během průtrže.

### 2. Series 21. Year - P. save the bubble!

A submarine has dived into deep ocean in Marian ditch and released a bubble of air. It started to go to surface. However, when you calculate, using gas equation, density of the air, you will see that it is bigger than density of water. Is it possible?

If you agree, explain your answer. If you do not agree, calculate what will be parameters of the bubble (mainly density).

Úlohu navrhla Lenka Zdeborová.

### 1. Series 21. Year - 2. save the bubble!

Batyscaphe Trieste dived into deep sea and released a bubble which started to come to the surface. What is the vertical speed of the bubble? How will this speed change? How long it will take to reach surface? What size of bubbles will be fastest?

Úlohu vymyslel Jano Lalinský.

### 3. Series 19. Year - 4. rising current

A plane is flying horizontally at speed $v$ and suddenly enters into a rising current (jet) of speed $v′$. What will be acceleration of the plane just after entering the jet?

Assume the buoyancy coefficient $C$ (coefficient in Newton' equation for buoyancy) is linearly proportional to the angle between air flow and wing plane.

Navrhl Matouš Ringel, když mu úlohu odmítl prof. Volf.

### 2. Series 19. Year - E. fluffy cream

Measure pressure of gas in pressurised CO_{2} container used for home making of sparkling lemonade from still water. The container is filled with CO_{2} or is filled with N_{2}O for fluffy cream preparation.

Kájínek vyčetl na internetu.

### 3. Series 18. Year - E. density of air

Measure the density of air. Use any method but do not forget to provide relevant theory. The correct answer should contain also estimation of experimental error.

### 2. Series 18. Year - 3. helicopter

For helicopter to levitate it needs motor of power P. What is the power P' of the helicopter, which is scale copy of the previous one in scale 1:2? Assume the effectiveness of the rotor to be 100%.

Úloha byla převzata z MFO v Kanadě.

### 1. Series 18. Year - P. anti-rocket

Assume a container on wheels with an orifice on the side. If the container is filled with compressed air, then the air escapes out and whole container moves. It is same principle as the rocket engines. Assume inverse situation – the container with vacuum inside in room full of air. How will the container move? The container can move without friction.

1. ročník 1.kolo.