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Q1. Explain why are holes made in hoardings and banners?

Solution

Air exerts pressure in all directions. If hoardings and banners do not have holes on them then the pressure exerted by wind may tear off or make them fall. Holes let the air pass through it thus reducing the air pressure on hoardings and banners.

Q2. Why summer monsoon winds are known as south west monsoon winds?

Solution

This is because summer monsoon winds blow from south west part of India towards south Asia.

Q3. How tornadoes cause destruction?

Solution

Tornadoes cause destruction in the following ways: a.The central core of low pressure creates a suction which can blow off roofs and make house collapse. b.The violent winds can damage the strongest man made structures.

Q4. List any one basic difference between tornado and cyclone.

Solution

One basic difference between tornado and cyclone is that tornado develops over land while cyclone develops over sea.

Q5. What are the post cyclone measures that should be taken?

Solution

1. Strictly avoid any loose and dangling wires. 2. Do not drink water that could be contaminated. Always store drinking water. 3. Do not go out for emergencies. 4. Cooperate and help your neighbours and friends.

Q6. Write the precautions to be taken if you are staying in a cyclone hit area.

Solution

Precautions to be taken if you are staying in a cyclone hit area

• Do not drink water that could be contaminated.
• Store drinking water that can be used during emergencies.
• Do not touch wet switches and fallen power lines.
• Do not go out for the sake of fun.
• Do not pressurize the rescue force by making undue demands.
• Cooperate and help your neighbours and friends. 

Q7. (i) How winter monsoon winds cause rainfall in Tamil Nadu?(ii) Why land breeze blows during night?

Solution

(i) Winter monsoon winds blow from Indian landmass to sea, some of it pass over bay of Bengal and cause rainfall on coastal areas of Tamil Nadu.(ii) Land breeze blows during night because a. Land looses heat quickly and cools down so there is high air pressure on land. b. Water retains heat for a longer time so low air pressure develops over land.

Q8. Why both polar winds and westerlies blow towards 60 degree N and 60 degree S latitude?

Solution

Polar winds blow from high pressure on poles to temperate region as there is low air pressure. Westerlies are the hot winds which rise from equator and get cools and come down and then blow towards temperate region. So, both polar winds and westerlies blow towards 60 degree N and 60 degree S latitude.

Q9. Why the smoke rises up?

Solution

The smoke rises up because the warm air is lighter than the cold air.

Q10. (i) Why monsoon winds are known as seasonal winds?(ii) Why sea breeze blow during day?

Solution

(i) During the months of June to September due to high temperature, sea breeze blows from sea to land which carry high amount of moisture and cause rainfall in India. So, these are known as summer monsoon winds. (ii) Sea breeze blows during day because a.Land gets heated quickly so low pressure develops over land. b.Water takes time to heat so high pressure is over the water.

Q11. Why wind blows from a region of high air pressure to low pressure area?

Solution

Due to unequal heating of earth, air expands and rises up creating a low pressure area. To maintain the balance in air pressure, air from a region of high pressure blows towards low pressure area. Thus, the wind blows from a region of high pressure to low pressure area.

Q12. What is wind and its causes?

Solution

Moving air is called wind. Air moves from a high pressure region to low pressure region. It is caused due to the difference in air pressure between two places.

Q13. What are the main reasons for the movement of air?

Solution

Wind blows from a region of high pressure to low pressure due to: a.Unequal heating of earth. b.Difference in air pressure.

Q14. Explain the uneven heating between the equator and the poles. 

Solution

The air in the equatorial regions is warmer as this region recieves maximum heat of the Sun. This warm air rises creating a low pressure region. Now, the poles (or the region above 30 degree latitude on both sides) recieves lesser heat and so the air in those regions is cooler. As the warm air rises, the cooler air from the poles moves in to take its place thereby creating a flow of wind from the northern and southern regions to the equator. Hence, the uneven heating of the Earth causes a wind flow pattern on Earth.

Q15. Why is cyclone the most destructive natural calamity?

Solution

Cyclone is the most destructive natural calamity because it last longer and affects a wider area.

Q16. What is the main cause for the development of storm?

Solution

The main cause for the development of storm is unequal heating of the surface of earth.

Q17. Explain formation of thunderstorms in your words?

Solution

Due to unequal heating of earth surface, air gets heated up soon due to which the following sequence of events takes place: a. Air pressure decreases. b. Hot moist air rises up. c. Condensation occurs and clouds are formed. d. More heat is released as a result clouds rise up. e. Water droplets become heavy and fall on earth as rain. f. Hot air also gets cool and comes down speedily and warm air rises. This is accompanied by thunder and lightning.

Q18. Describe an experiment to show that pressure reduces when air moves with high speed.

Solution

1. Hold a 20 cm long and 3 cm wide paper strip between your thumb and forefinger.                                   2. Blow air over the paper. 3. Ensure fingers do not obstruct the flow of air while blowing. 4. It is noticed that the paper is lifted up instead of going down. 5. Harder we blow, higher it rises up. This is because the blowing air over the strip causes reduction in pressure. 

Q19. Why tornadoes are also known waterspouts?

Solution

When tornadoes develop over sea, it sucks up a huge column of water and are known as waterspouts.

Q20. Why does a balloon expand when you blow air into it? Why does it make a noise when it's popped?

Solution

When a balloon is blown up, the air pressure inside the balloon slowly becomes greater than the air pressure outside the balloon. Since the balloon is made of rubber and is expandable, it grows larger and larger. When the balloon is popped, the air escapes instantly. The sound heard is due to the molecules of air inside the balloon coming into sudden contact with the molecules of air outside the balloon.

Q21. Give reasons : Ventilators are situated close to the ceiling.

Solution

Hot air is lighter than cold air. Hence, the air that is hot rises upwards and the cold air settles down. The ventilators are situated at the top inorder to let the rising hot air out of the house and the cooler air takes its place inside the house from the windows.

Q22. Can air pressure tell us about the kind of weather to expect?

Solution

Yes, air pressure can tell us about what kind of weather to expect. If a high pressure system is on its way, often we can expect cooler temperatures and clear skies. If a low pressure system is coming, then we look for warmer weather, storms and rain.

Q23. When is a storm expected?

Solution

When the pressure difference between two areas is very high then cool air rushes at very high speed towards low pressure area. In such a condition storm is expected.

Q24. Define cyclone.

Solution

A cyclone is a huge and powerful storm. It consists of a low pressure area with high pressure all around. High speed winds go around the centre violently and are accompanied by heavy rains.

Q25. What preventive measures could be taken during a cyclone?

Solution

1. Always store drinking water for emergencies. 2. Do not touch wet switches and fallen power lines. 3. Cooperate and help your neighbours and friends.

Q26. Why winds do not flow in straight N-S direction?

Solution

Because earth rotates from west to east direction. Therefore, winds blow in an easterly direction.

Q27. When we are flying a kite, then the wind coming from our back side helps. Give reason.

Solution

When we are flying a kite, then the wind coming from our back side helps because wind from back side strikes the kite and exerts pressure on it to make it fly higher.

Q28. How satellites are helpful in predicting weather patterns?

Solution

Weather satellites take pictures of clouds, measure temperature, wind speed and wind directions. Thus, they help in predicting weather patterns.

Q29. How cyclones are formed?

Solution

Due to unequal heating of sea, warm air rises up creating a low air pressure region. Cold air rushes in, which forces up more hot air and the current of air sets up. Due to rotation of earth, cold air swirls around the low pressure area.

Q30. How the tornadoes blow off roofs during storm?

Solution

During tornadoes, winds moves speedily and thus a low pressure is created above the roofs in comparison to lower surface due to which an up thrust acts over them and thus, tornadoes blow off roofs during storm.

Q31. How can a person save himself from tornado?

Solution

Following measures could be taken: a. They should move to basement. b. If caught outdoors, one should get out of vehicles and lie in a ditch.

Q32. Write a short note on the structure of a cyclone.

Solution

Structure of a Cyclone The centre of a cyclone is called the eye of the storm. This is a calm region. The diameter of the eye varies from 10-30 km. This region is free of clouds and has light winds. Around this clear eye there is a cloud region of about 150 km. In this region, there are high-speed winds and thick clouds with heavy rains. As we move away from this region, the wind speed decreases.

Q33. What  is the meaning of wind flow pattern?

Solution

The surface of the Earth close to the equators gets maximum sunlight and the poles get the least amount of sunlight. Hence, there is an uneven heating of the Earth. This causes the warm air from the equatorial region to rise up and the cold air from the polar region rush to take the place of warm air. This causes wind to flow on Earth. Now, due to rotation of Earth, the wind curves and does not flow exactly from North to South. This flow of the wind acquires a pattern on Earth called the wind flow pattern of Earth.

Q34. How thunderstorm claim more lives than cyclones?

Solution

Though cyclones are most destructive but a large number of people lose their lives due to lightning during thunderstorm. Thus, thunderstorm claims more lives than cyclones.

Q35. Can thunderstorm develop when the air is dry?

Solution

No, because rain is typical characteristic of thunderstorm and rain will not occur if sufficient water vapours are not present in air.

Q36. Why land breeze blows during night?

Solution

Land breeze blows during night because a.Land looses heat quickly and cools down so there is high air pressure on land. b.Water retains heat for a longer time so low air pressure develops over land.

Q37. How cyclone affects marine life and soil?

Solution

Cyclones have the following effects: a. Due to cyclones many marine organisms get killed and it also destructs coral reefs. b. It brings sea water and thus makes soil saline which makes the soil unfit for cultivation.

Q38. In which areas thunderstorms develop frequently?

Solution

Thunderstorms develop frequently in areas having tropical climate.

Q39. What is atmospheric pressure?

Solution

Atmospheric pressure is the air pressure which is exerted by the weight of air present in the atmosphere.

Q40.  In what ways atmospheric pressure is similar to liquid pressure?

Solution

Atmospheric pressure is similar to liquid pressure in the following ways: 1. Both of these pressures act in all directions. 2. Both of these pressures become less as we rise up through air or liquid. Atmospheric pressure is similar to liquid pressure in the following ways: 1. Both these pressures act in all directions. 2. Both these pressures become less as we rise up through the liquid or air.