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

The correct statement is:

(i) In winter the winds flow from the land to the ocean.

Correct option is (iii).

Explanation:

Indian coastline regions are most vulnerable to cyclones.

The experiences which show that air exerts pressure are as follows:

1. Blowing air in a balloon exerts pressure on its walls and causes it to inflate.
2. Paper bits spread on a cardboard moves and show displacement when air is blown over them.

The direction of wind can be found by following two methods:

1. Hold a small piece of cloth and raise your hand high in the air. The cloth will flow in the direction of the wind.
2. Pick some sand in your fist and allow it to fall slowly. The direction of fall of sand is same as that of the wind. This method of determining the direction of wind is widely used in desert areas by the travellers.

Holes are made in hanging banners and hoardings in order to equalise the air pressure on both sides of them. Higher pressure on one side of the hanging banners and hoardings may blow or torn them away when wind blows from one side at a high speed. Presence of holes allows air to pass through and prevents building up high pressure on one side.

One should not buy a house having windows but no ventilators because this interrupts cross-ventilation in the house. Cool fresh air enters the house through windows while dispensed heated air generated due to various human activities like, cooking, breathing etc; is removed through ventilators. Heated air being light rises up towards the roof and takes route through ventilators towards outside.

Given steps should be followed in advance to deal with the situation created by a cyclone:

1. An efficient weather forecast and warning system should be in place for timely action.
2. Rapid communication systems like, TV, radio etc, should be geared up for giving warnings to government agencies, ports, ships and fishermen in advance.
3. Cyclone management centres should be constructed in cyclone prone areas.
4. Rescue teams should be formed in advance for rapid shifting of people to safer places.
5. Safe drinking water and eatables should always be kept stored for providing relief in emergencies.

In case of cyclone approaching our village or town, we can help our neighbours in following ways:

• Making them aware of the warnings issued by the meteorological department through TV, radio, or newspapers.
• Advising them to choose safer places to shift whenever necessary and make arrangements to move essential household goods, domestic animals and vehicles, etc.
• Circulating the phone numbers of all emergency services like police, fire brigade and hospitals to all.
• Asking them to avoid travelling on roads with standing water, as floods might have damaged the roads.
• Storing sufficient amount of drinking water and eatables for emergencies.
• Extending cooperation to all for meeting the state of emergency.

(a) Wind is moving air.

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

(c) Near the earth’s surface hot air rises up whereas cool air comes down.

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