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## gas mechanics

### 2. Series 9. Year - P. wind in mines

Great Russian scientist M.V. Lomonosov in his work „On the Free Movement of Air in Mines“ discovered the causes of the permanent streams of air in mines of type shown on pic. 4. Determine their direction on condition the air temperature in the mine is constant during the year and the same in all points of the mine.

### 1. Series 9. Year - 4. gas pressure

A gas of temperature $t$ is placed in a vessel with walls the temperature of which is $t_{c}$. In what case is the gas pressure on the walls higher: when we warm the walls above or when we cool them bellow the gas temperature?