Topic outline

    • Winds, Storms and Cyclones

      Q19. Why is it easier to row the boat if there is wind coming from behind you?

      Ans. It is easier to row the boat if there is wind coming from behind us because it exerts pressure on the boat in the same direction in which boat is moving.


      Q20. What is the difference between a Cyclone, Typhoon, and Hurricane?

      Ans. A cyclone is known by different names in different parts of the world. It is called a ‘hurricane’ in the American continent. In Philippines and Japan it is called a ‘typhoon’.


      Q21. What is a tornado?

      Ans. A tornado is a dark funnel shaped cloud that reaches from the sky to the ground. Most of the tornadoes are weak. A violent tornado can travel at speeds of about 300 km/h. Tornadoes may form within cyclones.


      Q22. Which regions of India are vulnerable to cyclones?

      Ans. The whole coastline of India is vulnerable to cyclones, particularly the east coast. The west coast of India is less vulnerable to cyclonic storms both in terms of intensity and frequency of the cyclones.

      Q23. How does air move?

      Ans. Air moves because of difference in air pressure. Air moves from the region where the air pressure is high to the region where the pressure is low. The greater the difference in pressure, the faster the air moves.


      Q24. Explain why smoke always rises up?

      Ans. On heating the air expands and occupies more space. When the same thing occupies more space, it becomes lighter. The warm air is, therefore, lighter than the cold air. That is the reason that the smoke goes up.


      Q25. Hold a strip of paper, 20 cm long and 3 cm wide, between your thumb and forefinger. Now blow over the paper. What do you think will happen to the paper? Give reason.

      Ans. When we blew over the paper strip, it went upwards. This could happen if blowing over the paper reduced the air pressure above the strip.


      Q26. List some effective safety measures for cyclone.

      Ans. Some effective safety measures are:

                                   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.

      Q27. Explain why holes are made in hanging banners and hoardings.

      Ans. Air exerts pressure. It is due to this pressure that the banners or hoardings flutter and torn when the wind is blowing. Holes are made in hanging banners and hoardings so that air can pass through these holes, which reduces the air pressure on the banners and hoardings.


      Q28. Why is it difficult to force the paper ball into the bottle?

      Ans. When we blow into the mouth of the bottle the air near the mouth has higher speed. This decreases the pressure there. The air pressure inside the bottle is higher than near the mouth. The air inside the bottle pushes the ball out. Thus, it is difficult to force the paper ball into the bottle.


      Q29. What are monsoon winds?

      Ans. In summer, near the equator the land warms up faster and most of the time the temperature of the land is higher than that of water in the oceans. The air over the land gets heated and rises. This causes the winds to flow from the oceans towards the land. These are monsoon winds.


      Q30. Suggest two methods to find out wind direction at a given place.

      Ans. Two methods to find out wind direction at a given place are:

                                  i.        Take some dry leaves and release it from height. The direction in which the leaves start flowing is the direction of wind.

                                 ii.        Wind vane, or weathercock is an instrument for showing the direction of the wind can be used to find out wind direction.

      Q31. ‘A bicycle tube overfilled with air may burst’. Give reason.

      Ans. Air is made up of tiny particles called ‘molecules’ which move around quickly in all directions. When we put air in a bicycle tube, the fast-moving air molecules ‘collide’ with the walls of the tube and exert a force on the walls of the tube from inside. The force produces pressure. When the pressure of air increases than the capacity of the tube, the tube may burst.

      Q32. What is thunderstorm?

      Ans. Thunderstorms develop in hot, humid tropical areas like India very frequently. The rising temperatures produce strong upward rising winds. These winds carry water droplets upwards, where they freeze, and fall down again. The swift movement of the falling water droplets along with the rising air creates lightning and sound. It is this event that we call a thunderstorm.

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