Topic outline

    • Winds, Storms and Cyclones

      Q33. Why are people advised not to stand near fast moving train?

      Ans. When train moves with high speed it creates region of low pressure. Therefore, the air pressure behind the person becomes bigger than the air pressure between the person and the train. Due to this pressure differences, the force acts on the person towards the train and push man towards the train. Thus, people are advised not to stand near fast moving train.


      Q34. What are the destructions caused by cyclones?

      Ans. As a result of cyclone, the seawater enters the low-lying coastal areas, causing severe loss of life and property. It also reduces the fertility of the soil. Continuous heavy rainfall may further worsen the flood situation. High-speed winds accompanying a cyclone can damage houses, telephones and other communication systems, trees, etc., causing tremendous loss of life and property.


      Q35. What would happen if high-speed winds blew over the roofs of buildings?

      Ans. If the roofs were weak, they could be lifted and blown away. This happens when high speed winds are blowing above the roof of a building; air pressure above the roof gets reduced. The air pressure inside the building is much more than the air pressure above the roof. This difference in the air pressure makes the roof be blown away.

      Q36. Take a soft plastic bottle. Fill it with hot water. Empty the bottle and immediately cap it tightly. Place the bottle under running water. Shape of the bottle gets distorted. Explain why the bottle gets distorted?

      Ans. As water is poured over the bottle, some steam in the bottle condenses into water, reducing the amount of air inside. The pressure of air inside the bottle decreases than the pressure exerted by the air from outside the bottle. As a result the can gets compressed.


      Q37. You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.

      Ans. As warm air rises, air pressure at that place is reduced and the cooler air moves to that place. This warm air goes out from the house mostly through ventilators. If a house does not have ventilators then the warm cannot go out easily and circulation of air will not happen. Hence, I would not prefer a house having windows but no ventilators.


      Q38. How will you help your neighbours in case cyclone approaches your village/town?

      Ans. I will help my neighbours in case cyclone approaches our village/town:

                               i.        By making them aware of cyclone forecast and warning service.

                              ii.        By helping them to shift the essential household goods, domestic animals and vehicles, etc. to safer places.

                             iii.        By calling emergency services like police, fire brigade, and medical centres in case of need.

      Q39. State two experiences that made you think that air exerts pressure (other than those given in the text).

      Ans.  Two experiences that made us think that air exerts pressure are:

      Experience 1: Fill up the tumbler with water up to the brim. Cover it with cardboard piece and turn the glass upside down. Slowly remove your hand. We will observe that cardboard does not fall and water stays in the glass. This happens as air pushes the cardboard up and prevents it from falling.

      Experience 2: When we blow air into the balloon the pressure inside the balloon increases and the balloon inflates to increase its surface area.


      Q40. What planning is required in advance to deal with the situation created by a cyclone?

      Ans. The following planning is required in advance to deal with the situation created by a cyclone.

                                i.        A cyclone forecast and warning service.

                               ii.        Rapid communication of warnings to the Government agencies, the ports, fishermen, ships and to the general public.

                              iii.        Construction of cyclone shelters in the cyclone prone areas, and Administrative arrangements for moving people fast to safer places.

      Q41. Explain the formation of a cyclone.
      What is a cyclone?

      Ans. Before cloud formation, water takes up heat from the atmosphere to change into vapour. When water vapour changes back to liquid form as raindrops, this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low-pressure system with very high-speed winds revolving around it. It is this weather condition that we call a cyclone.

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