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The pressure of the atmosphere

To inflate a balloon by stretching the rubber skin you must blow air into it.
As a high altitude balloon goes up it gets bigger.
It is very difficult to pour liquid out of a tin if only one small hole is made in the tin but much easier if another hole is made in the tin on the opposite side of the lid.
A rubber sucker can me made to stick to a flat surface

We live at the bottom of an ocean of air we call it the ATMOSPHERE. It presses on us from all directions, and it's only the pressure of our blood and the air in our bodies that stops parts of us from being squashed. If we think of the air in the atmosphere to be like a liquid then our ocean of air would be about 8000 m deep! Obviously if we lived at the bottom of an ocean of 8000 m of water the pressure would be enormous so the density of air must be much lower than that of water.

The pressure of the air at sea level is about 100 000 N/m2 (Pa). This is like having two quite heavy people standing on your head.

You can show the effects of air pressure either by trying to move something through the air or by looking at the effect of air pressure on an object containing no air.

© Keith Gibbs 2011