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प्रश्न
Describe an activity to demonstrate that warm air is lighter than cool air
उत्तर
(i) Take two same sizes of empty paper bags.
(ii) On the two ends of a wooden stick hang both of the bags in an upturned position.
(iii) In the centre of the stick tie a portion of the thread.
(iv) According to figure (A), hold the stick by the thread in balance.
(v) According to figure (B), place the burning candle below one of the bags.
(vi) Now, you will observe an unbalanced stick. This represents that as the warm/temperate air rises up and it pushes the bag over the candle.
(vii) Now we can say that when air is heated, it expands and also occupies more space. So, we can conclude that warm air is lighter as compared to cool air.
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संबंधित प्रश्न
Following are precautions one must take in case a storm is accompanied by lightning.
(i) Do not take shelter under a tree.
(ii) Do not take shelter under an umbrella with a metallic end.
(iii) Do not take shelter in open garages, storage sheds, etc.
(iv) Do not take shelter in a bus in the open.
Which one of these is not correct?
Air around us exerts __________ .
The moving air is called _________ .
State whether the following statement is True or False:
Warm air is lighter than cool air.
To expel hot air out of the kitchen, ‘A’ has an exhaust fan fitted on the window of her kitchen and ‘B’ has a similar exhaust fan fitted on the wall near the ceiling of her kitchen. Which of the exhaust fan will expel the hot air more effectively? Explain why?
Match Column I with Column II. There can be more than one match.
| Column I | Column II | ||
| (a) | on heating air | (i) | descends |
| (b) | on cooling air | (ii) | expands |
| (iii) | contracts | ||
| (iv) | rises | ||
The picture in Figure 8.4 shows a tree line along the sea coast on an island near the equator. As shown, the treetops are permanently bent in one direction. Are the trees bent towards the sea or away from it? Explain.
