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  • 22 August 2018

    NCERT STD 7 SCIENCE UNIT 8 Wind Storm and Cyclones UNIT TEST PDF FILE

    Wind Storm

    Air: Air is a mixture of gases.
    Wind: Moving air is called wind.
    Air exerts pressure: The fact that Air exerts pressure can be understood by many examples.
    • Tube of bicycle gets inflated when air is filled in it. This happens because air exerts pressure.
    • It is difficult to move the bicycle against the direction of wind. Similarly, a sailor feels it difficult to sail his boat against the direction of wind. This happens because air exerts pressure.
    • When boiled water is filled in a tin can and its mouth is closed with the lid; followed by cold water being poured over it, the can gets distorted. This happens because air inside the can gets condensed and creates low pressure. The higher pressure from outside distorts the shape of the can.
    • You can fly a kite because air exerts pressure from the rear portion of the kite.
    • Aeroplane can fly because air exerts pressure.
    • Birds can fly because air exerts pressure.
    • High speed wind creates area of low air pressure:
    • Thatched roof is blown off because of high speed wind. This happens because high speed wind creates an area of low pressure. Due to this, the thatched roof is sucked up and finally gets blown away. Thus, increase in wind speed is associated by decrease in air pressure.
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    By Nikunj Savani

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