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

The blanks can be filled as follows, based on the principles of atmospheric science:

(a) Wind is moving air. Wind is essentially the movement of air from one place to another.

(b) Winds are generated due to uneven heating on the earth. Different parts of the Earth receive different amounts of solar radiation, leading to temperature variations.

(c) Near the earth's surface warm air rises up whereas cooler air comes down. Warm air is less dense and rises, while cooler air is denser and sinks.

(d) Air moves from a region of high pressure to a region of low pressure. This pressure gradient is the fundamental driving force behind wind generation.

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

1. Using light materials: You can take a small amount of fine sand or a piece of light paper and gently release it from your palm. The direction in which the sand or paper moves indicates the direction the wind is blowing.
2. Flying a kite: A kite naturally flies in the direction the wind is pushing it. Therefore, the direction in which the kite flies will show the wind direction.

Additionally, instruments like a wind vane or an anemometer are specifically designed to indicate wind direction and speed.

Here are two experiences that demonstrate air exerts pressure:

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 against or with the wind: It is noticeably more difficult to ride a bicycle when cycling against the wind compared to cycling in the direction of the wind. This difference in effort is due to the pressure exerted by the wind pushing against you when you move into it.

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

Ventilators play a crucial role in air circulation within a room. Warm air inside a house, especially from sources like kitchens or from body heat, tends to rise. If there are no ventilators, this warm air has no easy escape route. Consequently, it can accumulate, making the room uncomfortably hot and potentially leading to a feeling of suffocation or discomfort. Windows provide light and can be opened for ventilation, but ventilators offer a continuous, passive way for warm air to exit, complementing the function of windows for better overall air quality and comfort.

Holes are made in hanging banners and hoardings to reduce the pressure exerted by the wind. Air exerts pressure in all directions. When strong winds blow against a large, flat surface like a banner or hoarding, they can exert a significant force. If the banner or hoarding is solid, this wind pressure can be strong enough to tear it apart, damage its supports, or even cause it to fall. By creating holes, the wind can pass through the material, thereby reducing the overall pressure acting on the banner or hoarding. This makes the structure more stable and less likely to be damaged during windy conditions.

In the event of an approaching cyclone, helping neighbours and the community is vital. Here's how I would assist:

• Assisting with Relocation: I would help neighbours and friends move their important household items, livestock, and vehicles to safer locations, away from potential flood or wind damage.
• Communication and Information: I would help communicate with emergency services like the police, fire brigade, and medical centres if needed, and share reliable information about the cyclone's progress and safety instructions.
• Resource Management: I would ensure that neighbours have access to safe drinking water, perhaps by helping to store it properly or share available supplies.
• Safety Awareness: I would advise neighbours to avoid travelling on roads near flood-affected areas and to stay indoors or in designated safe shelters.

The principle of 'self-help is the best help' extends to community support during such emergencies.

Effective planning in advance is crucial for dealing with the aftermath of a cyclone. Here are the key steps:

• Emergency Kit: Prepare and keep an emergency kit at home containing essential items like a first-aid kit, flashlight, batteries, and any necessary medications.
• Food and Water Storage: Store sufficient food in waterproof bags or containers to last for several days. Ensure a supply of safe drinking water, as water sources can become contaminated after a cyclone.
• Emergency Contacts: Keep a list of important phone numbers readily accessible, including those for emergency services (police, hospital, fire brigade), as well as friends and relatives who can provide assistance.
• Securing Valuables: Make arrangements to shift essential household goods, domestic animals, and vehicles to safer, elevated, or protected locations to minimize damage.
• Information and Awareness: Stay informed about weather forecasts and cyclone warnings from official sources and ensure family members know the safety procedures.

Being prepared can significantly reduce the impact of a cyclone and aid in a quicker recovery.