Fill the missing word in the blank spaces in the following statements:
(A) Wind is _______________ air.
(B) Winds are generated due to _______________ heating on the earth.
(C) Near the earth’s surface _______________ air rises up whereas _______________ air comes down.
(D) Air moves from a region of _______________ pressure to a region of _______________ pressure.
(A) moving, (B) uneven, (C) warm; cooler, (D) high; lowQ 2.
Suggest two methods to find out wind direction at a given place.SOLUTION:
(i) The direction of moving wind can be detected by an instrument called the weather vane or wind vane. This arrow-shaped vane is mounted at its centre to move freely about its vertical. The arrow aligns itself and its tip points towards the direction of the wind. Four directions—North, South, East and West—are marked on the wind vane. For obtaining the accurate direction, the wind vane is mounted high above the ground so that it is free from obstacles such as tall trees and high buildings.
(ii) Take a handful of soil in your hand. Allow it to fall from your hand. It will flow in the direction in which wind is blowing.
State two experiences that made you think that air exerts pressure (other than those given in the text).SOLUTION:
(i) If we take water upto the brim of a glass and place a piece of cardboard over the top of the glass.
Now holding the cardboard in place over a sink, on turning the glass upside down. We remove our hand gently away from the cardboard. We notice that due to air pressure, cardboard does not fall from below. This keeps the water in the glass. It is because of air pressure being exerted on the cardboard.
(ii) While riding a bicycle against direction of wind we can observe that air exerts pressure. We can feel it on our face.
You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.SOLUTION:
We would not like to buy a house having windows but no ventilators, as there will be no cross ventilation of air inside the house.
Fresh cool air entering the room through windows will get heated up because of various household activities like breathing, cooking, etc. This warm air will rise up inside the rooms. If there will be no ventilators near the ceiling of the house, the warm and impure air will have no passage to leave as the level of windows will be quite low from the level of warm air. This will lead to increase in room temperature as well as humidity. It will be very discomforting for human as it could cause suffocation.
Explain why holes are made in hanging banners and hoardings.SOLUTION:
Holes are made in hanging banners and hoardings so that air can pass through them easily and to reduce the air pressure. If banners and hoardings do not have holes, pressure exerted by wind may tear them off, loosen them or make them fall.Q 6.
How will you help your neighbours in case cyclone approaches your village/town?SOLUTION:
(i) Making them aware of cyclone forecast and warning service.
(ii) Rapid communication of warning to the government agencies and all the important places. (iii) Construction of cyclone shelters in the cyclone prone areas.
(iv) Helping people to shift essential goods, domestic animals etc. to safer places.
What planning is required in advance to deal with the situation created by a cyclone?SOLUTION:
Effective safety measures :
(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 shelter in the cyclone prone areas, and administrative arrangements for moving people far to safer places.
Which one of the following place is unlikely to be affected by a cyclone.
(i) Chennai (ii) Mangaluru (Mangalore) (iii) Amritsar (iv) Puri
(iii) As Amritsar is located far away from the sea.Q 9.
Which of the statements given below is correct?
(i) In winter the winds flow from the land to the ocean.
(ii) In summer the winds flow from the land towards the ocean.
(iii) A cyclone is formed by a very high-pressure system with very high-speed winds revolving around it.
(iv) The coastline of India is not vulnerable to cyclones.