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Chapter 5 Notes- PRESSURE and WIND

# Chapter 5 Notes- PRESSURE and WIND - PRESSURE and WIND Acts...

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PRESSURE and WIND Acts in all directions because the atmosphere is a gas. Example: the weight of air on the roof of a typical house is about 2,000,000 pounds, however the roof does not collapse because the same force acts on both the top and bottom of the roof. In the atmosphere as air is heated it expands. Because it expands it becomes less dense and therefore, rises. This creates an area of low pressure at the surface. As the warm air rises it begins to cool, eventually causing it to sink back to the surface creating an area of high pressure. In general, air flows towards areas of low pressure and away from areas of high pressure. Measurement of Pressure 1. Mercury barometer - the pressure air exerts on a column of mercury. At sea level this pressure averages 29.92 inches. 2. Aneroid barometer - uses a partial vacuum that expands or contracts as a function of changing atmospheric pressure. Same device as an altimeter in airplanes. Pressure is usually given in inches of mercury by television weathermen. But the National Weather Service reports pressure in millibars. For those scientists out there one millibar = 10 newtons. Wind Caused by pressure gradients. Wind is an attempt to equalize the pressure differential. This differential is the result of unequal heating of different portions of the Earth's surface.

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Chapter 5 Notes- PRESSURE and WIND - PRESSURE and WIND Acts...

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