Science 3 Marks Question

As the sun warms the Earth's surface, the atmosphere warms too. Some parts of the Earth receive direct rays from the sun all year and are always warm. Other places receive indirect rays, so the climate is colder. Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow.

The following planning is required to deal with the situation created by a cyclone.

1. Facilities for cyclone prediction and forecasting which can give cyclone warning in advance.
2. Quick information and communication linkages so that information can be spread quickly.
3. Construction of cyclone shelters and arrangement for moving people to safer places for safety during cyclone.

We have experienced that when we blow a balloon, the balloon becomes tight. If we try to fill more air, then the balloon will burst after an extent. This happens because air exerts pressure. We have also experienced the movement of fringes of windows and doors of our houses when wind blows in a high speed. This also happens because air exerts pressure.

In the given figure, the tree line along the sea coast on an island near the equator shows that tree tops are permanently bent in one direction, i.e. towards the land. The reason behind this movement of trees is that during the day time, the wind blows from sea to land because at this time, land gets warmer more quickly than sea. This makes the air of land, warm and lighter which is raised up in the sky. Therefore, the top of the bent trees shows the moving direction of wind from sea to land.

In a warm summer day along the coast, this differential heating of land and sea leads to the development of local winds called sea breezes. As air above the land surface is heated by radiation from the Sun, it expands and begins to rise, being lighter than the surrounding air. To replace the rising air, cooler air is drawn in from above the surface of the sea. This is the sea breeze, and can offer a pleasant cooling influence on hot summer afternoons.

A monsoon is a seasonal wind, found especially in Asia that reverses direction between summer and winter and often brings heavy rains. In the summer, a high pressure area lies over the Indian Ocean while a low exists over the Asian continent. The air masses move from the high pressure over the ocean to the low over the continent, bringing moisture- laden air to south Asia. During winter, the process is reversed and a low sits over the Indian Ocean while a high lies over the Tibetan plateau so air flows down the Himalaya and south to the ocean.

We would not buy a house having windows but no ventilators, as there will be no cross ventilation of air inside the room. Fresh cool Air entering the room through window gets heated through human and other household activities like breathing, cooking and become lighter, this warm air rises up inside the room. If there is no ventilator near the roof, the warm air will have no passage to leave as the level of window is quite low from the level of warm air. This will increase the room temperature as well as humidity inside leading to human discomfort.

During storms, heavy winds passing over the house creates a low pressure. The high pressure inside the house tries to fill the low pressure outside. Since, this pressure is stuck inside the house, therefore, it pushes or lifts the roof off.
So, unless the house is well ventilated, the roof is more likely to blow off in a strong wind.

The following are the two methods to find out the direction of wind.

1. While flying a kite, air exerts pressure on the kite due to which the kite flies. The direction in which the kite flies is the direction of blowing of wind.
2. While riding a bicycle, the direction in which it is difficult to ride is opposite to the direction of the blowing wind.

Therefore, while flying a kite or riding a bicycle, the wind direction at a given place can be determined.

1. When Rohan blows air into the balloon, the balloon gets inflated due to the pressure exerted by air. But, Rohan observed that most of his balloons burstd. The reason behind it was, he overfilled the air into the balloon. The warm air gets expanded inside the balloon and exerted more and due to the more pressure on the walls of the balloon, balloons burstd.
2. From the condition mentioned above, it can be concluded that air expands on heating.
3. Curiosity to learn and scientific attitude.

High speed winds and air pressure difference can cause cyclones.They are formed when water vapour changes back to liquid by the release of heat. This heat warms air around and it rises to move up and more air rushes to the vacant place. Thus, a cycle is formed which have low pressure and very high speed of air.

The banner and hoarding are generally having a large surface area and are put out side in open where they may subject to varying air pressure depending on wind conditions. If wind pressure is high, then air will exert a great amount of pressure on the banners or hoarding causing it to flutter or blown away. To prevent this, holes are made in hanging banner and hording, through which air pressure gets leaked causing less damage or fluttering to banners or hoarding.

The importance of air pressure can be discussed as follows:

1. It creates wind The difference in atmospheric pressure gives rise to the wind on the earth.
2. It influences weather Air movement, i.e. downward or upward movement of air, caused due to differences in pressure creates cloudy and clear sky, brings rain or fine weather.
3. Weather forecasting The changes in air pressure give important clues for weather forecasting. The air pressure is measured by an instrument called barometer.

We can find the wind direction using a Wind Vane or Weather Vane or Weather Cock. It consists of a flat metallic sheet generally cut into shape of a cock or arrow which is mounted on disk and free to move around a axial shaft and point in the direction of wind. They are typically used as an architectural ornament to the highest point of a building. Also we can find the direction of light wind using smoke from incense sticks. The direction of smoke will indicate the wind direction.

Yes, the following flow chart explains the phenomenon leading to the formation of cloud, rain, stornrand cyclone.

In case cyclone approaches, the neighbours should be helped in the following ways.

1. By helping in moving to cyclone shelters and other safer places.
2. By asking them to take necessary steps to shift animals, vehicles and household goods to safer places.
3. By calling the emergency services such as police, fire brigade and medical centres when required.