Ncert solutions for class 7 science chapter 8 Winds, Storms and Cyclones – with questions and answers, pfds, notes and extra questions and answers
Summary Ncert solutions for class 7 science chapter 8 Winds, Storms and Cyclones
Air exerts pressure
Under varying conditions and on all surfaces and in all directions, air exerts pressure in different ways. When the wind is blowing, air pressure helps the leaves of trees, banners or flags to flutter.
Importance of air pressure
- The difference in atmospheric pressure gives rise to the wind on the earth.
- It influences weather Air movement, i.e. downward or upward movement of air caused due to differences in pressure creates the cloudy and clear sky, brings rain or fine weather.
- Weather forecasting – The changes in air pressure gives important clues for weather forecasting. A barometer measures this.
When we pump air or fill air into the bicycle tube, the air molecules inside the tube collide with the walls of the tube and exerts air pressure. The air pressure exerted from inside inflates the bicycle tube. The pressure exerted by air filled in a bicycle tube keeps the tube tight and makes the bicycle tire feel hard. If we continuously fill more and more air into the bicycle tube, the air pressure in the bicycle tube will increase too much that tube may get burst. These observations also show that air exerts pressure.
High Speed winds
Reduced air pressure is followed by high-speed winds. Air travels from the higher pressure area to the lower pressure area. The bigger the pressure gap, the quicker the air travels. It is due to the heat of the sun that causes a low pressure under which air becomes humid. So, the warm air rises and the cold air falls towards the sea from the surrounding area.
The fast-moving air blowing over an object helps in lifting the object up by producing a region of low pressure above it.
Air expands on heating
The term ‘expansion of air’ means the increase in the volume of air. When air is heated, its volume increases and occupies a bigger space. This is the reason that when we burn woods, the smoke rises along with the hot air near the place of fire.
The wind is the movement of air which depends on the difference in air pressure in two regions. Air moves from the region of high pressure to the region of low pressure in the atmosphere. The difference is created by unequal heating on the earth. The region where the air rises, an area of low pressure is created while the region where the air sinks, an area of high pressure is created.
The uneven heating on the earth takes place in two situations:
- Uneven Heating between the Equator and the Poles
- Uneven Heating of Land and Water
Thunderstorms are produced by the dark clouds which form at fairly low altitude in the atmosphere. In the tropical area, the air gets warmed up and makes it to rise, whereas humidity provides the water vapour for the formation of cloud.
Therefore, it can be said that to occur a thunderstorm, it requires moisture, rapidly rising warm air and sea breeze or mountains.
A cyclone is a weather condition consisting of a system of high-speed winds revolving around a central area of very low pressure. Cyclones develop over tropical seas. It is a violent storm with a wind speed of 150-250 km/h. It is accompanied by strong winds and heavy rains.
Cyclones are very destructive. These are the greatest storm on earth. Cyclones cause widespread destruction and loss of life in coastal areas. When the strong winds push water towards the shore even if the storm is hundreds of kilometre away, it gives the first indication of an approaching cyclone.
A tornado is a violent spinning storm in the shape of a dark funnel with a narrow end on the land.
These are formed over the sea and are called water spouts. Tornado develops from the thunderstorm and is formed mostly on the land. These are violent and can reach the speeds of more than 500 km/h destroying everything in their path. These are not very common in India but occurs in Canada and the USA.
Use of technology
During the early part of the last century, the people residing in coastal regions have less than a day for the preparations or to evacuate their homes from an overcoming cyclone. But, today’s situation is very different.
Today we are much protected. There are satellites and radars which can issue the cyclone watch or cyclone alert before 48 hours (in advance) of any expected storm and a cyclone warning is issued 24 hours in advance.
Therefore, coastal residents have sufficient time to prepare and evacuate their homes. The message related to the cyclone is broadcasted over the ratio every hour or half hour when a cyclone is nearer the coast.
In this way, the advanced technology has helped us in giving better protection from cyclones. Several national and international organisations cooperate to monitor cyclone-related disasters.
Conclusion – Ncert solutions for class 7 science chapter 8 Winds, Storms and Cyclones
Ncert solutions for class 7 science chapter 8 Winds, Storms and Cyclones have been provided along with questions and answers.
Questions and Answers – Ncert solutions for class 7 science chapter 8 Winds, Storms and Cyclones
1. 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) Wind is moving air.
(b) Winds are generated due to uneven heating on the earth.
(c) Near the earth’s surface, warm air rises up whereas cold air comes down.
(d) Air moves from a region of high air pressure to a region of low air pressure.
2. Suggest two methods to find out wind direction at a given place.
Methods to finding out the wind direction at a given place are as follows
i. By seeing the direction of dry leaves released in the air.
ii By seeing the direction in which it is difficult to ride the bicycle.
Short Answers – Ncert solutions for class 7 science chapter 8 Winds, Storms and Cyclones
3. State two experiences that made you think that air exerts pressure (other than those given in the text).
i. When we fill the air in the balloon, it becomes tight and if we try to fill more air balloon will get burst which proves air exerts pressure.
ii. Wind causes curtains, doors and windows to move with the direction of the wind. This demonstrates air exerts pressure.
4. You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.
It is not a good idea to buy a house without ventilators because warm air is lighter than cold air hence warm air passes out of your home through ventilators. Accordingly, without ventilators, warm air will not pass out, and the house will remain warm.
5. Explain why holes are made in hanging banners and hoardings.
Holes in the banners and hoardings helps air to pass through it. Hence, banner can withstand the pressure of the air and remains intact.
Short Answers – Ncert solutions for class 7 science chapter 8 Winds, Storms and Cyclones
6. How will you help your neighbours in case cyclone approaches your village/town?
We can help our neighbours in case a cyclone approaches, by any of the following measures:
- Help them shift to a safer place.
- By helping them to shift their animals, necessary households and vehicles to a safer place.
- By calling emergency services such as fire station, police and medical centres.
7. What planning is required in advance to deal with the situation created by a cyclone?
- We should not ignore the warnings issued by the meteorological department through TV, radio, or newspapers.
- We should — make necessary arrangements to shift the essential household goods, domestic animals and vehicles, etc. to safer places;
- Avoid driving on roads through standing water, as floods may have damaged the roads.
- Phone numbers of all emergency services like police, fire brigade, and medical centres should be handy.
- Always store drinking water for emergencies.
- Do not touch wet switches and fallen power lines.
- Do not pressurise the rescue force by making undue demands.
- Cooperate and help your neighbours and friends.
8. Which one of the following places is unlikely to be affected by a cyclone?
(ii) Mangaluru (Mangalore)
The answer is (iii) Amritsar because Amritsar is far away from the sea while the remaining three are coastal areas and are more likely to be hit by cyclone.
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.
The answer is (i) In winter, the winds flow from the land to the ocean.