CBSE Class 7 Science Chapter 8: Winds, Storms and Cyclones NCERT Solutions

The completed statements are:

(a) Wind is moving air.

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

(c) Near the earth's surface warm air rises up whereas cooler air comes down.

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

Explanation: Wind is essentially the movement of air. This movement is driven by differences in temperature and pressure caused by the uneven heating of the Earth's surface. Warm air, being less dense, rises, creating an area of low pressure, while cooler, denser air sinks, creating an area of high pressure. Air naturally flows from high-pressure areas to low-pressure areas.

Two simple methods to determine the direction of the wind are:

1. Using a kite: Fly a kite. The direction in which the kite flies indicates the direction of the wind.
2. Using a piece of paper: Take a small, light piece of paper and hold it out on your palm. The direction in which the paper is pushed or flies away shows the direction the wind is blowing.

Other methods include observing the movement of dust particles or using a wind vane or anemometer.

Two everyday experiences that demonstrate air exerts pressure are:

1. Fluttering leaves and branches: When the wind blows, tree leaves and branches move and flutter. This movement is caused by the force, or pressure, exerted by the moving air (wind) on them.
2. Cycling difficulty: It is noticeably harder to ride a bicycle when cycling against the wind compared to cycling with the wind. This difference in effort is due to the air pressure pushing against the cyclist and bicycle when moving into the wind.

No, I would prefer a house with both windows and ventilators. Here's why:

Ventilators, typically placed higher up, allow warm air and smoke (which rise because they are less dense) to escape from the room. If a house only has windows and no ventilators, especially in areas like the kitchen where smoke and warm air are generated, this warm air would have difficulty escaping. Without an outlet, the warm air would accumulate, making the room hotter, potentially uncomfortable, and could even lead to suffocation.

Holes are made in hanging banners and hoardings to reduce the effect of air pressure exerted by the wind. When strong winds blow, they exert considerable pressure on large, flat surfaces like banners. If these banners do not have holes, the wind pressure can be strong enough to tear them apart or even pull them down. By incorporating holes, the wind can pass through the banner, distributing the pressure more evenly and significantly reducing the risk of damage.

In the event of an approaching cyclone, I would help my neighbours in the following ways:

• Assisting with relocation: Help neighbours move their important household items, livestock, and vehicles to safer, elevated locations to protect them from potential flooding and wind damage.
• Communication and Information: Stay in touch with government agencies like the police, fire brigade, and medical services to relay information and request assistance if needed.
• Water storage: Encourage and help neighbours store adequate amounts of safe drinking water in waterproof containers, as water sources may become contaminated.
• Avoiding hazardous areas: Advise neighbours to avoid travelling on roads near flood-prone areas or those that might be damaged by the cyclone.
• Community support: Offer emotional support and share resources with neighbours, fostering a sense of community resilience.

Advance planning is crucial for effectively dealing with a cyclone. Here are the key preparations required:

• Emergency Kit: Assemble and keep an emergency kit at home containing essential supplies like a first-aid kit, flashlight, batteries, whistle, and any necessary personal medications.
• Food and Water Storage: Store sufficient non-perishable food items in waterproof bags or containers. Ensure a supply of safe drinking water, as tap water may become contaminated or unavailable.
• Emergency Contacts: Keep a list of important phone numbers readily accessible, including those for emergency services (police, hospital, fire brigade), utility companies, and close friends or relatives.
• Securing Belongings: Make arrangements to shift essential household goods, domestic animals, and vehicles to safer, more secure locations, preferably higher ground, before the cyclone hits.
• Information Awareness: Stay informed about weather updates and cyclone warnings from reliable sources like meteorological departments and local authorities.

Being prepared in advance ensures a quicker and safer response when a cyclone threat is imminent.