Class 7 Science
Question 1: Fill the missing word in the blank spaces in the following statements:
(a) Wind is——————air.
(b) Winds are generated due to——————heating on the earth.
(c) Near the earth’s surface __________air rises up whereas ___________ air comes down.
(d) Air moves from a region of ——— pressure to a region of——— pressure.
Answer: (a) moving, (b) uneven, (c) warm, cold, (d) high, low
Question 2: Suggest two methods to find out wind direction at a given place.
Answer: Two methods to find the direction of wind:
- Take a handful of sand or dust. Release it slowly from a height and observe the direction in which the falling sand is moving. This will show the direction of wind.
- Tie a thin plastic sheet or cloth with a stick. Keep the stick at a place which is as high as possible. The direction in which the cloth sways shows the direction of wind.
Question 3: State two experiences that made you think that air exerts pressure (other than those given in the text).
Answer: I have seen paratroopers jumping from aeroplanes. The parachute helps them in reaching the ground safely. The air pressure reduces the speed of the parachute and the paratrooper lands without getting injured.
Question 4: You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.
Answer: A house should have ventilators along with windows. The warm air would rise up and exit from the ventilators. The cooler air would rush in through the windows. This will help in making the rooms comfortable. A room without ventilators shall not be cooled as efficiently as one with ventilators.
Question 5: Explain why holes are made in hanging banners and hoardings.
Answer: Banners and hoardings are usually very large. The air pressure; because of the moving air; can blow away the banners. Holes are made in banners and hoardings so that the wind can move through them. This helps in reducing the impact of air pressure on the hoardings and thus they are not blown away.
Question 6: How will you help your neighbours in case cyclone approaches your village/town?
Answer: I will take following steps to help my neighbours in case of cyclone:
- I will help people to reach to a safer place.
- I will organize a community kitchen during the stress period.
- I will provide first aid to injured people.
- I will also arrange for safe drinking water for the people.
Question 7: What planning is required in advance to deal with the situation created by a cyclone?
Answer: Following planning is required to deal with the situation created by a cyclone:
- Proper shelters should be built by the government agencies so that people can be accommodated in them.
- Alternate arrangements of seamless communication among rescue agencies should be made.
- Proper stock of emergency medicines should be kept.
- Proper arrangements of safe drinking water should be made.
- Government should chalk out a rehabilitation plan for those affected by cyclone.
Question 8: Which one of the following place is unlikely to be affected by a cyclone?
(i) Chennai (ii) Mangaluru (Mangalore) (iii) Amritsar (iv) Puri
Answer: (iii) Amritsar
Question 9: Which of the statements given below is correct?
- In winter the winds flow from the land to the ocean.
- In summer the winds flow from the land towards the ocean.
- A cyclone is formed by a very high-pressure system with very high-speed winds revolving around it.
- The coastline of India is not vulnerable to cyclones.
Answer: (i) In winter the winds flow from the land to the ocean