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Theory:

Air is required for all living things to survive in the world. One can live without food and water for a few days, but no living being can survive without air.
 
We can indeed feel the presence of air even though we cannot see it. We can notice its presence in our day-to-day life while flying a kite, swaying clothes, fluttering pages of a book, winnowing, and rustling trees.
 
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Flying kite
 
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Swaying clothes
 
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Winnowing
 
During storms, the trees get uprooted, and the rooftops even get blown away due to the violent air movement.
 
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Storm
Air is a mixture of many gases. The various components present in the air are nitrogen, oxygen, carbon-di-oxide, water vapour, dust particles and some other gases.
Wind:
Moving air is known as wind.  It can be soothing as a breeze (gentle wind), and sometimes it can even be violent.
A firki is a good example that shows the movement of air. A firki rotates when it is held in an open area in the direction of the wind.
 
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Firki
 
Weather prediction:
A weathercock helps to show the direction in which the air moves. It is very useful in predicting the weather of a place.
 
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Weathercock
 
Like a weathercock, a windsock is also used to find the wind's direction.
 
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Windsock