NCERT Class 7 Science Chapter 8 Winds, Storms and Cyclones

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NCERT Class 7 Science Chapter 8 Winds, Storms and Cyclones

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Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 7 Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 7 Science Chapter 8 Winds, Storms and Cyclones and Textbook for All Chapters, You can practice these here.

Winds, Storms and Cyclones

Chapter: 8

NCERT TEXT BOOK EXERCISES

Q. 1. Fill the missings words in the blank spaces of the following statements:

(a) Wind is _________ air.

Ans: Moving.

(b) Winds are generated due to _________ heating on the earth.

Ans: Uneven.

(c) Near the earth’s surface _________ air rises up whereas _________ air comes down. 

Ans: Warm, cooler

(d) Air moves from a region of _________ pressure to a region of _________ pressure. 

Ans: High, low.

Q. 2. Suggest two methods to find out wind direction at a given place.

Ans: (i) Take a piece of paper in your hand. Allow it to fall from your hand. It will blow in the direction in which wind is blowing.

(ii) You can also use a wind vane (a device helps us to make accurate measurement of wind direction) to find out the direction of wind.

Q. 3. State two experiences that made you think that air exerts pressure (other than those given in the text).

Ans: (i) Balloons and balls can be used only when they are inflated with air. 

(ii) Compressed air is used in the brake system for stopping trains.

Q. 4. You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer. 

Ans: No. A house which has no ventilators is not a healthy house to live in. The air circulation is not there in such a house and hence it has no fresh air.

Q. 5. Explain why holes are made in hanging banners and hoardings.

Ans: Air exerts pressure. It is due to this pressure, banners and hoardings flutter when the wind is blowing. Holes are made in the banners and hoardings as wind pass through that holes and they do not become loose and fall down.

Q.6. How will you help your neighbors in case cyclone approaches your village/ town?  

Ans: (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.

Q. 7. What planning is required in advance to deal with the situation created by a cyclone? 

Ans: In order to deal with cyclone, it is important to follow the following points: 

(i) listening carefully to warnings being transmitted on TV and radio.

(ii) moving to safer places or taking adequate steps to ensure safety at home.

(iii) keeping an emergency kit ready.

(iv) storing food in water-proof bags. 

(v) not venturing into sea.

(vi) keeping all the emergency telephone numbers handy.

Q.8. Which one of the following place is unlikely to be affected by a cyclone?

(i) Chennai 

(ii) Mangalore 

(iii) Amritsar

(v) Puri.

Ans: (iv) Puri.

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.

Ans: (i) In winter the winds flow from the

land to the ocean.

ADDITIONAL IMPORTANT QUESTIONS

Very Short Answer Questions 

Q. 1. When cold water is poured over a tightly corked tin can containing steam, the tin gets crushed. What crushes the tin can?

Ans: Atmospheric pressure.

Q. 2. What conclusion do you get from the observation that when cold water is poured over a tin can full of steam and corked tightly, the tin gets crushed? 

Ans: Air around us exerts pressure.

Q.3. Which of the two is associated with his speed winds: reduced air pressure or increased air pressure?

Ans: Reduced air pressure.

Q. 4. What name is given to the winds which blow off from the Indian ocean during summer?

Ans: Monsoon.

Q. 5. Which of the two are more frequent in India: cyclones or tornadoes?

Ans: Cyclones.

Q. 6. What is the name of a storm consisting of a column of rapidly rotating air and having the appearance of a funnel shaped cloud whose lower end touches the ground?

Ans: Tornado.

Q. 7. Which area of a cyclone is calm, free of clouds and has only light winds? 

Ans: Centre of cyclone called eye of cyclone.

Q.8. Due to uneven heating of ‘land’ and ‘ocean’ water:

(a) in which season do winds blow from land towards ocean?

Ans: Winter season.

(b) In which season do winds blow from ocean towards land?

Ans: Summer season. 

Q. 9. What is the main cause of wind?

Ans: The air moves from the region where the air pressure is high to those regions where the air pressure is low.

Q. 10. What happens when temperature is increased at a place? 

Ans: On heating the air expands and becomes lighter.

Q. 11. What are the factors which contribute to the development of cyclones? 

Ans: Wind speed, wind direction, temperature and humidity contribute to the development of cyclones.

Q. 12. What is called the eye of the storm? 

Ans: The center of a cyclone in a calm area is called the eye of the storm.

Q. 13. What is wind vane?

Ans: An instrument used to find the direction of the wind is called wind vane.

Q. 14. Why is warm air lighter than cold air?

Ans: Due to expansion, air occupies more space (or volume). As a result, density decreases and it becomes lighter. Thus warm air is lighter than the cold air.

Q. 15. What are cyclone shelters?

Ans: Structures built in cyclone prone areas to withstand high speed wind forces are called cyclone shelters.

Short Answer Questions

Q. 1. The mouth of a balloon is stretched and fixed tightly over the neck of an empty boiling tube. When the boiling tube is placed in a beaker containing hot water, the balloon fixed over the neck of boiling tube gets inflated. Why?

Ans: The empty boiling tube contains air. This air expands on heating and inflates the balloon.

Q. 2. Why hot air goes up?

Ans: When we heat the air then it expands and occupies large space. We know that when same thing occupies space, it becomes lighter. The warm air is therefore lighter than the cold air. It is because hot air goes up.

Q. 3. State two observations (or experiences) which tell us that air exerts pressure.

Ans: (i) When air is filled into a balloon with our mouth, the balloon gets inflated. 

(ii) When air is filled into a bicycle tube with a pump, the bicycle tube gets inflated and makes the bicycle feel hard. 

Q.4. Explain why, when air is filled into a balloon, the balloon get inflated? 

Ans: When we fill air into the bicycle tube, then the air molecules inside the tube collide with the walls of the tube and exert pressure. This air pressure exerted from inside, inflates the bicycle tube.

Q. 5. Explain why, a bicycle tube overfilled with air may burst?

Ans: A bicycle tube overfilled with air, the air pressure in the bicycle tube will increase too much due to which the bicycle tube may burst.

Q. 6. Explain why, smoke always rises up.

Ans: Smoke is produced by the burning of a substance, therefore, smoke is always accompanied by hot air (or warm air). Since warm air is lighter than the cold air, therefore, smoke contained in warm air always rises up.

Q. 7. Would you like to buy a house having windows but no ventilators? Explain your answer. 

Ans: We should buy a house having windows as well as ventilators. The windows are for bringing in fresh air from outside into the house. The ventilators (located near the roof of house) take out the warm and stale air from inside the house. The presence of ventilators in the house increases our comfort.

Q. 8. How does atmospheric pressure influence weather?

Ans: (i) Low atmospheric pressure is associated with cloudy sky and wet weather. 

(ii) High atmospheric pressure is associated with clear and sunny sky.

Q. 9. What are tornadoes? Where do the tornadoes occur frequently?

Ans: A tornado is a violent spinning storm in the shape of a dark funnel with a narrow end of the land. Tornadoes develop from thunderstorms and are formed mostly on land. Most of the tornadoes are weak but a violent tornado can travel with a speed of about 300 km/h. Tornadoes are not very frequent in India but frequently occur in Canada and USA.

Q. 10. A tin can is full of steam and a tight lid is put on it. What will happen if cold water is poured over this tin can? Give reason for your answer.

Ans: The tin can gets crushed. On passing cold water, the hot steam cools and gets condensed to form water due to which pressure inside the tin can is reduced too much. The large air pressure acting on the tin can from outside crushes the tin can inwards.

Short Answer Questions 

Q. 1. Mention any three damaging effects caused by cyclones.

Ans: (i) Cyclones push water and produce water waves causing floods.

(ii) The low pressure in the eye of the cyclone lifts water to a height of upto 12 m. It appears like a wall of water. This water wall enters low lying coastal areas and causes severe loss of life and property.

(iii) High speed winds of a cyclone can damage buildings, telephone and electricity system.

Q. 2. Mention three safety measures against cyclones. 

Ans: (i) People should follow the guidelines provided by the agencies through TV, Radio, Internet etc., for their safety against cyclone. 

(ii) Do not drive on roads which are under water. The flood might has damaged the road. 

(iii) Keep ready the phone numbers of all emergency services, e.g. Police, Fire Brigade, Hospital etc.

Q.3. What are monsoon winds? Why are monsoon winds very important for our country?

Ans: Monsoon winds are the seasonal winds which blow from the Indian ocean towards the Indian subcontinent in one season and then. retreat from land towards the sea in the other season of the year.

Monsoon is the lifeline for the Indian subcontinent. It provides us plenty of water for agriculture activities.

Q.4. How are summer monsoons caused over India?

Ans: Monsoon winds are well developed over the Indian subcontinent in southern Asia. During summer season, the interior of the continent gets heated rapidly forming a region of low pressure. This low pressure attracts winds from the Indian ocean in the south. These warm moist winds blowing from the seas to the land are the summer monsoon.

Q. 5. What is an anemometer? Give its construction and working.

Ans: An anemometer is used to measure wind speed. Anemometers come in a variety of forms, but the simplest type is the cup anemometer. It consists of vertical pole with four horizontal arms attached to the cup. Cups are attached to the ends of the four arms. Wind causes the cups to rotate the arms around the vertical pole. If wind is blowing very fast, then the speed with which the cups rotate will increase.

Fig. 8.16. An anemometer for measuring the speed of wind.

Long Answer Questions

Q. 1. How are wind currents generated? 

Ans: Wind currents are generated due to uneven heating on the earth. Depending on the locations involved two situations are possible.

(i) Uneven heating between the equator and the poles: The air in the polar region is colder than at latitude 30° – 60°. Thus the warm air from 30° – 60° belt moves up and the colder air moves down from the polar regions. Such movements of air from warmer to the colder and from the colder to warmer regions give rise to wind currents.

(ii) Uneven heating of the land and water on the earth : Uneven heating of the land and water on the earth also causes wind currents.

Q. 2. How does atmospheric pressure influence weather?

Ans: Upward movement of air causes cloudy and the downward movement of air causes clear sky.

As air rises and creates an area of low pressure, water vapour in it condenses to form clouds. Conversely, sinking air generally means that condensation cannot take place.

(i) Low pressure is, therefore, associated with cloudy skies and wet weather. 

(ii) High pressure is therefore associated with clear and sunny skies.

Q. 3. What precautions would you take it you are facing a storm with lightning? 

Ans: The following precautions should be taken when we are facing a storm with lightning: 

(i) If you are in forest, take shelter under a small tree. Do not lie on the ground. 

(ii) Do not take shelter under an umbrella with a metallic end.

(iii) Do not sit near a window. Open garages, storage sheds, metal sheds are not safe places to take shelter. 

(iv) A car or a bus is a safe place to take shelter.

(v) If you are in water, get out and go inside a building.

HOT QUESTIONS

Q. 1. Out of equator, 30 N latitude and 60 N latitude: 

(a) Which region has the coldest air?

Give reason for your answer in each case.

Ans: 60° N latitude has the coldest air because it is nearer to the north pole of the earth than 30° N latitude.

(b) Which region has the warmest air?

Ans: Equator has the warmest air because equator is at the minimum distance from the sun. 

Q. 2. Which one of the following pines is unlikely to be affected by a cyclone? Why?

(a) Chennai. 

(b) Mangaluru (Mangalore). 

(c) Amritsar. 

(d) Puri. 

Ans: Amritsar is unlikely to be affected by a cyclone because a cyclone develops over a sea and Amritsar is very far away from the sea.

Q. 3. How are the cyclone warnings issued?

Ans: The cyclone warnings are issued in two stages. The first stage warning known as cyclone alert or cyclone watch is issued 48 hours in advance of the expected beginning of the adverse weather over coastal areas. The second stage warning known as eyelone warning is issued 24 hours in advance through wireless network.

SKILL BASED QUESTIONS

1. Observe the following figure and answer the following questions:

(i) Label the marks: (1) and (2) 

(ii) What is the result of this activity? 

Ans: (i) (1) Paper cup, (2) Burning candle.

(ii) The activity shows that hot air becomes lighter and rises up.

Fig. 8.17.

2. Draw a diagram to show uneven heating of land generates monsoon winds from south-west direction in summer. 

Ans: 

Fig. 8.18. Uneven heating of land especially the Rajasthan desert generates monsoon winds from southwest direction in summer. 

These winds carry lots of water from the Indian Ocean.

FORMATIVE ASSESSMENT

1. Fill in the following blanks with suitable words:

(i) Moving air is called _________.

Ans: Wind.

(ii) A bicycle tube becomes tight on filling air because air exerts ___________.

Ans: Pressure.

(iii) Air ________ on heating and ______ on cooling. 

Ans: Expands, expands.

(iv) Warm air is __________ than cold air.

Ans: Lighter.

(v) Near the earth’s surface _________ air rises up whereas ________ air causes down.

Ans: Warm, cold.

(vi) Low pressure is associated with _________ sky and _______ weather.

Ans: Cloudy, wet.

(vii) __________ are generated due to ________ heating of the earth. 

Ans: Wind currents uneven.

(viii) The wind flowing from the _______ to

________ usually brings _________.

Ans: Ocean, land, rain.

(ix) During thunderstorm, do not take shelter under _________.

Ans: An isolated tree.

(x) Cyclones of the temperate latitude are called ____________.

Ans: Depressions.

2. State whether the following statements are true or false:

(i) A car or bus is not a safe place to take shelter during lightning.

Ans: False.

(ii) The coastline of India is not vulnerable to cyclones. 

Ans: False.

(iii) A cyclone is formed by a very low pressure center with very high speed winds revolving around it.

Ans: True. 

(iv) The eye of a cyclone has a very high air pressure.

Ans: False.

(v) The funnel of a tornado sucks dust, debris and everything near it at the base due to low pressure and throws them out near the top.

Ans: True.

(vi) The region from where the air rises, an area of low pressure is created. 

Ans: True.

(vii) During winters, the wind flows from the land towards the ocean.

Ans: True.

(viii) Wind currents are generated due to uneven heating on the earth.

Ans: True.

(ix) A cyclone is formed by a very high pressure system with very high speed winds revolving around it.

Ans: False.

(x) Thunderstorm is only associated with heavy rainfall.

Ans: False.

3. Matching Type Questions: Match the columns:

Ans:

4. Multiple Choice Questions:

(i) Wind is not caused due to:

(a) uneven heating between equator and poles 

(b) air pressure

(c) due to uneven heating of land and water

(d) difference in humidity 

Ans: (d) Difference in humidity.

(ii) Increased wind speed:

(a) increases air pressure

(b) does not affect air pressure humidity

(c) reduces air pressure 

(d) lowers humidity

Ans: (c) Reduces air pressure.

(iii) The center of cyclones is called

(a) eye

(b) water spouts

(c) storm-surge

(d) head.

Ans: (a) Eye.

(iv) Tropical cyclones that originate in the China sea are:

(a) hurricanes 

(b) typhoons

(c) tornadoes

(d) cyclones

Ans: (b) Typhoons.

(v) Which of the following plays a major role in the formation of a thunderstorm?

(a) Conduction 

(b) Convection

(c) Radiation

(d) All of the above

Ans: (b) Convection.

(vi) The winds from oceans carry water and bring rain are called:

(a) cyclone 

(b) typhoon

(c) monsoon

(d) none of the above

Ans: (c) Monsoon.

(vii) Which of the following places is likely to get affected by a cyclone?

(a) Delhi

(b) Jaipur

(c) Amritsar

(d) Puri

Ans: (d) Puri.

(viii) Formation of a thunderstorm requires:

(a) moisture 

(b) rapidly rising warm air

(c) sea breeze

(d) all of the above 

Ans: (d) All of the above.

(ix) Which of the following contributes to the development of cyclones?

(a) wind speed 

(b) temperature

(c) humidity

(d) all of the above

Ans: (d) All of the above.

(x) Precautions to be observed during a thunderstorm when you are inside:

(a) Do not sit near the open window

(b) Do not operate any electrical appliance

(c) Do not watch T.V.

(d) All of the above

Ans: (d) All of the above.

5. Write one word for the following:

(i) The atmospheric layer at a height of 50 km to 80 km.

Ans: Mesosphere.

(ii) Movements of air from warmer to the colder or from colder to warmer regions. 

Ans: Wind currents.

(iii) The swift movement of the falling water along with the rising warm air producing sound, lightning.

Ans: Thunderstorms.

(iv) A small low pressure system with very high speed winds revolving around it.

Ans: Cyclone.

(v) The calm area at the center of a cyclone. 

Ans: Eye of the cyclone.

(vi) The air moving from regions of high pressure to regions of low pressure.

Ans: Wind.

(vii) A system of wind which moves away from the sea towards the land in the latitudes of 5° to 30°.

Ans: Monsoon.

(viii) A region of warm and moist air which is at a lower pressure than the surrounding atmosphere.

Ans: Low pressure.

(ix) A brilliant flash of light formed during thunderstorm due to the discharge of electrically charged clouds. 

Ans: Lightning.

(x) Structures built in cyclone prone areas to withstand high speed wind forces.

Ans: Cyclone shelters.