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CBSE Sample Paper Class 7 Science Winds, Storms and Cyclones
Chapter 8
winds, storms and cyclones
Multiple choice questions: (marks:1×3)
1.) The instrument that measures the wind speed is called:
A.) Thermometer
B.) Anemometer
C.) Barometer
Ans: Anemometer.
2.) The word monsoon is derived from the………word ‘Monsoon’.
A.) Arabic
B.) Latin
C.) French
Ans: Arabic.
3.) A violent tornado can travel at the speed of about:
A.) 100km/hr
B.) 200km/hr
C.) 300km/hr
Ans: 300km/hr.
Fill in the blanks: ( marks: 1×3)
1.) Air moves from the………….region to…………. region.
Ans: high pressure, low pressure.
2.) ………….carries the water and it rains.
Ans: The monsoon rain.
Answer the following questions: (marks:1×2)
1.) What is called the wind?
Ans: The moving air is called the wind.
2.) What are the contributory factors to the development of cyclones?
Ans: The contributory factors to the development of cyclone are: wind speed, wind direction, temperature and humidity.
Answer the following questions: (marks: 2×6)
1.) Explain why the warm air is lighter than the cold air?
Ans: When the air is heated it 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.
2.) What is called a 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 create lightning and sound. It is this event that we call a thunderstorm.
3.) What is known as the eye of the storm?
Ans: The centre of a cyclone is a calm area. It is called the eye of the storm. A large cyclone is a violently rotating mass of air in the atmosphere, 10 to 15 km high. The diameter of the eye varies from 10 to 30 km. It is a region free of clouds and has light winds. Around this calm and clear eye, there is a cloud region of about 150 km in size. In this region there are high-speed winds (150–250 km/h) and thick clouds with heavy rain. Away from this region the wind speed gradually decreases.
4.) What is a cyclone?
Ans: Before cloud formation, water takes up heat from the atmosphere to change into vapour. When water vapour changes back to liquid form as raindrops, this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low- pressure system with very high-speed winds revolving around it. It is this weather condition that we call a cyclone.
5.) What is called a 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 the Philippines and Japan it is called a ‘typhoon’.
6.) What are tornadoes?
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.
7.) What are the protecting measures that should be taken during a tornado?
Ans: During a tornado some precautionary measures should be taken:
- A tornado shelter is a room situated deep inside or underground having no windows.
- It is better to shut windows and take shelter under a table, workbench, where debris cannot reach.
- One has to bow down on knees protecting the head and neck using arms.
Answer the following questions: (marks: 5×3)
1.) What is a thunderstorm? What precautionary measures should be maintained when a storm with lightning occurs? (2+3)
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 create lightning and sound. It is this event that we call a thunderstorm.
If a storm is accompanied by lightning, we must take the following precautions:
- Do not take shelter under an isolated tree. If you are in a forest, take shelter under a small tree. Do not lie on the ground.
- Do not take shelter under an umbrella with a metallic end.
- Do not sit near a window. Open garages, storage sheds, metal sheds are not safe places to take shelter.
- A car or a bus is a safe place to take shelter.
- If you are in water, get out and go inside a building.
2.) What are the effective safety measures taken in case of a cyclone?
Ans: Cyclones can be very destructive. Strong winds push water towards the shore even if the storm is hundreds of kilometres away. These are the first indications of an approaching cyclone. The water waves produced by the wind are so powerful that a person cannot overcome them. Some effective safety measures should be taken if cyclones occur:
- A cyclone forecast and warning service.
- Rapid communication of warnings to the. Government agencies, the ports, fishermen, ships and to the general public.
- Construction of cyclone shelters in the cyclone prone areas, and
- Administrative arrangements for moving people fast to safer places.
Action on the part of the people:
- 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; and keep ready the phone numbers of all emergency services like police, fire brigade, and medical centres.
Some other precautions for the people staying in a cyclone hit area:
- Do not drink water that could be contaminated. Always store drinking water for emergencies.
- Do not touch wet switches and fallen power lines.
- Do not go out just for the sake of fun.
- Do not pressurise the rescue force by making undue demands.
- Cooperate and help your neighbours and friends.
3.) Write down about the formation of a storm and cyclone?
Ans: Before cloud formation, water takes up heat from the atmosphere to change into vapour. When water vapour changes back to liquid form as raindrops, this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low- pressure system with very high-speed winds revolving around it. It is this weather condition that we call a cyclone. The following flow chart will help you to understand the phenomena that lead to the formation of clouds and falling of rain and creation of storms and cyclones: