What is Wind, Storms and Cyclones? NCERT Class 7 Science
Wind Storms and Cyclones – NCERT solutions for class 7 – In this article, we will study Online What is Wind, Storms and Cyclones? and How air exerts pressure? from Chapter – 8 of Class 7.
Air – It is a mixture of gases
Wind – The moving air is called wind. Since air is a mixture of gases and wind is the flow of gases on a large scale. Winds are caused by the heating difference between different parts of the world and the movement of the earth.
Winds can be of classified on the basis of:
- Duration: Long and Short
- Strength: High, medium and low
- Speed: Slow and Fast
High strength winds for a longer duration, like cyclone or hurricanes, may cause hazardous effects.
- Applications of wind include Windmills (to generate electricity), fan, flying kite, Hair Dryer etc.
How air exerts pressure?
Atmospheric pressure is the pressure exerted by the weight of air in the atmosphere of Earth (or that of another planet).
- All gases in the atmosphere exert pressure on each other, the earth and the objects on earth including humans.
- The pressure exerted on a human body by the atmosphere is compensated by the pressure exerted by the gases inside the human body.
- The force or the pressure exerted by air/wind makes loose paper, hair, flags, leaves of trees
- Manual tasks like riding a bicycle or rowing boat against the wind require more muscular energy, than normal, due to the opposing pressure exerted by the wind. Similarly, if riding and rowing are being done in the direction of the wind, then these tasks require less muscular energy than normal.
Examples to prove air exerts pressure
1. Inflation of bicycle tube
2. Hard to move a bicycle against the direction of the wind.
3. Birds can fly due to air exerts pressure.
Movement of air/ Air pressure concept –
Air moves from high-pressure zone to low-pressure zone of air. The greater the pressure difference, greater will be the speed of the wind and vice versa. Two major concepts are
- High-speed winds are accompanied by reduced air pressure.
- Air travels from high-pressure areas to low-pressure areas.
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Cause of Wind Movement
1. The pressure difference in air
Wind movement is created on the earth due to the pressure difference in the air caused by differential heating.
Warm air rises up because it becomes lighter. This creates an area of low pressure below the rising air. The area of low pressure is quickly filled in by the cooler air from around.
2. Uneven heating on earth Uneven heating on earth cause movement in the air. The air near the equatorial region gets heated as it gets the highest amount of sunshine during the year. The wind movement occurs as warm air rise and creates an area of low pressure and cooler air from the higher altitude rushes through the equator to fill the gap.
3. Uneven heating of land and water
Near sea breeze in coastal areas the land gets warm and the warm air rises up and creates the area of low pressure near the ground. The low-pressure zone is filled with cooler air from the ocean surface which gives rise to the sea breeze.
Land Breeze In the night, the land cools down faster than the ocean surface. The warm air rises up and creates an area of low pressure near the surface. The low-pressure zone is filled with cooler air from the land which gives rise to the land breeze.
Click another topic of 7th Class Science –
What is Weather, Climate, and Factors affecting climate?
Monsoon – Monsoon winds refer to the flow of air from the ocean towards land in summer. Monsoon has been derived from the Arabic word “
Thunderstorm – When rain falls with lightning, it is called thunderstorm. It occurs in hot and humid tropical areas like India. In the summer the air rises up along with lots of moisture. After rising up to a certain height water vapor cools down and starts coming down in the form of water droplets. The swift drifting of water droplets creates electricity among cloud. This manifests in the form of lightning and sound which refers to the thunderstorm.
The fast-moving air towards a center, usually with heavy rain is known as a cyclone. It is created with wind direction, wind speed, humidity, and temperature. When water vapor in the clouds cools down it releases heat. This heat warms the air around the clouds. The warm air rises up and creates a low-pressure zone. The low-pressure zone is quickly filled in by cooler air from the surrounding. This creates a system in which the center is having very low pressure and is surrounded by wind moving around it. The wind from the surrounding moves in a circular fashion towards the center and give rise to the cyclone. The center of the cyclone is called the eye.
Structure of Cyclone The structure of cyclone contains:
- Eye – Low pressure and area of sinking air. Its diameter ranges from 10-100 kms.
- Eye Wall – Dense cloud surrounding eye having maximum wind speed. It causes maximum destruction.
- Spiral rain bands – Band of clouds spiraling into eyewall and it contains heavy rains
The destruction caused by cyclone
Damage to the telephone poles, house, and electric poles and uproot trees.
It can cause high waves.
It can lift water up to 3 to 15 meters high which appears like a waterfall. This waterfall when pushed toward seashore can cause huge loss of life and property.
It causes Tornadoes; a fastest moving dark cloud in the shape of a funnel. Its speed is very violent and can go u to 300km.
1. some action should be taken by the government and other agencies like
– warning service 24 to 48 hours in advance.
– Rapid communication to the government
– Construction of cyclone shelter area in the cyclone-prone areas
– Shifting people to a safe place.
2. Action by other people
– Pay attention to warning forecast
– Stock necessary food and items in case of cyclone warnings.
– Move to a safer place.
– Help the rescue team
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Tag: NCERT Solutions for Class 7 Science, 7th Class, Wind, Storms and Cyclones, Cause of Wind Movement, How air exerts pressure?