Why does atmospheric pressure exist

Air has weight so the atmosphere consisting of tremendous amount of air has enormous weight. Atmospheric pressure is the air pressure which is exerted by the weight of air present in the atmosphere.

Atmospheric pressure is due to the weight of air present in the atmosphere above us. Atmospheric pressure also acts in all directions. On the surface of earth, the atmospheric pressure is maximum at the sea level. This is because the column of air above us is tallest at the sea level.

The atmospheric pressure on the surface of earth is As we go up in the atmosphere from the surface of earth ,the atmospheric pressure goes on decreasing. This is because as we go up in the atmosphere ,the weight air above us goes on decreasing. So the atmospheric pressure on the top of a hill mountain will be much less than at its base. The common unit for expressing and measuring atmospheric pressure is millimetres of mercury.

The atmospheric pressure on the surface of earth is mm of mercury. Activity : The existence of atmospheric pressure. A glass tumbler is filled to the brim with water and covered with a piece of thick and smooth card.

We press the card hard so that there is no air in the glass tumbler. Keeping the card in position with one hand we invert the glass tumbler full of water.

Any droplets that might lead to the formation of clouds would tend to evaporate. The end result tends to be a clearer and drier environment. Conversely, if we decrease the air pressure, the air tends to rise into the higher levels of atmosphere where temperatures are colder. As the capacity to hold water vapor diminishes, the vapor rapidly condenses and clouds which are composed of countless billions of tiny water droplets or, at very high altitudes, ice crystals will develop and ultimately precipitation will fall.

Of course, we could not forecast zones of high and low pressure without employing some sort of device to measure atmospheric pressure. Atmospheric pressure is the force per unit area exerted by the weight of the atmosphere. To measure that weight, meteorologists use a barometer. It was Evangelista Torricelli, an Italian physicist and mathematician who proved in that he could weigh the atmosphere against a column of mercury.

He actually measured pressure converting it directly to weight. The instrument Torricelli designed was the very first barometer. The open end of a glass tube is placed in an open dish of mercury. Atmospheric pressure forces the mercury to rise up the tube.

At sea level, the column of mercury will rise on average to a height of Why not use water instead of mercury? The reason is that at sea level, the water column would be about 34 feet high! Mercury on the other hand, is 14 times denser than water and is the heaviest substance available that remains a liquid at ordinary temperatures. That permits the instrument to be of a more manageable size. Such an instrument is called an aneroid barometer, which consists of a partially evacuated metal cell that expands and contracts with changing pressure and is attached to a coupling mechanism that drives an indicator the arrow along a scale graduated in pressure units, either in inches or millibars.

This would all seem logical, except it is all rather simplistic. It impacts the way people dress each day and the types of structures built. Explore weather and its impacts with this curated collection of classroom resources. An atmosphere is the layers of gases surrounding a planet or other celestial body. These gases are found in layers troposphere, stratosphere, mesosphere, thermosphere, and exosphere defined by unique features such as temperature and pressure.

The atmosphere protects life on earth by shielding it from incoming ultraviolet UV radiation, keeping the planet warm through insulation, and preventing extremes between day and night temperatures.

The sun heats layers of the atmosphere causing it to convect driving air movement and weather patterns around the world. Teach your students about the Earth's atmosphere with the resources in this collection.

A barometer is a tool used to measure atmospheric pressure, also called barometric pressure. An altimeter is a device that measures altitude, the distance of a point above sea level. Students conduct a series of experiments to see how water depth affects pressure.

They then develop a model to illustrate how pressure increases in deeper water. Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. A barometer measures atmospheric pressure, which is also called barometric pressure.

Celsius scale. Fahrenheit scale. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

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