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www.GOALias.blogspot.com8Winds, Storms and CyclonesOrissa was hit by a cyclone withwind speed of 200 km/h on18 October 1999. The cyclonesmashed 45,000 houses making7,00,000 people homeless. On29 October the same year, a secondcyclone with wind speed of 260 km/hhit Orissa again. It was accompanied bywater waves about 9 m high. Thousandsof people lost their lives. Property worthcrores of rupees was destroyed. Thecyclone affected agriculture, transport,communication, and electricity supply.Fig. 8.1 Image taken by a satellite of a cycloneapproaching the coast of OrissaCourtesy: India Meteorological Department,New Delhi80But, what are cyclones? How arethey formed? Why are they sodestructive? In this chapter we shallseek answers to some of these questions.We begin with some activitiesinvolving air. These activities will clarifysome basic features concerning acyclone. Before we begin, remember thatthe moving air is called the wind.8.1 A8.1 AIREXERTSPRESSUREActivity 8.1Whenever an activity involves heating,be very careful. It is advised that suchactivities are performed in thepresence of an elderly person fromyour family. Or, carry out theseactivities in the presence of yourteacher.You need to boil water in the followingactivity.Take a tin can with a lid. Fill itapproximately half with water. Heat thecan on a candle flame till the water boils.Let the water boil for a few minutes. Blowout the candle. Immediately put the lidtightly on the can. Be careful in handlingthe hot can. Put the can carefully in ashallow metallic vessel or a washbasin.Pour fresh water over the can.What happens to the shape of the can?SCIENCE